


TEACHERS' 
GEOGRAPHY 




Class . 
Book. 



• c 



Copyright N°_ 



COPYRIGHT DEPOSIT 



TEACHERS' GEOGRAPHY 



MAN AND CLIMATE 

WITH PRACTICAL EXERCISES 



SEVENTH PRINTING 



MARK JEFFERSON 

Michigan State Normal College 



Pubbhed by th* Author al 

YPSILANT1 MICHIGAN 

1916 



G-73 

.04 
1116 



Copyright, 1916, by Mark Jefferson 



APR -5 1916 



M ©H.A427549 



PURPOSE 

These notes arc planned to facilitate the work of the Teachers' course for 
the student by putting in his hand a statemenl of principles that will be ampli- 
tied and illustrated in the class room, and formulating the illustrative exercises 
he is t< perform. 

The work is a Teachers' Course in the State Normal College. That means 
that it i< 12 weeks of work thought essential to the professional preparation of 
the teacher who can give but one term to this department. The time period is 
not deliberate choice, but traditional. The 12 weeks' course is our unit. Given 
that unit it has seemed most prudent to subdivide the professional work into: 
1. The Teacher-*' Course, and 2. Regional Geography; (a) Geography of 
America, (b) Geography of Kurope. We wisli our students to have a modern 
point of view in geography. We have therefore to treat of the principles in- 
volved in modern doctrine on the subject. The time limitation narrows this 
course to a portion of the subject matter; the distribution of Man, Climate, 
which is the tir>t controlling condition of that distribution, and the construc- 
tion of simple map-. 



Where People Live. 

1. If Geography i rned with the earth and man, as soon as we have some 

n of land and water on our globe, it i oi interesl to IcnoM 

where this man ia A glance at the maps on pages it and IS ia nec< it this point 

The depth of shades on it corresponds to the den the population of the various 

the map ia black the homes of m< lose together, and vill 

aiu l ir ever; mile- in direction, many men living in 

little Tin- lighter shades, the ruled lines, correspond t«> regions where 

rcer and even towns and villages come at much wider intervals, and Farm 
e so Ear irom neighbors and so lonely that the people arc much less ac< us 
tomed to meeting people ami exchanging ideas with them. The dotted parts of the 
regions oi still fewer inhabitants, long stretches "i wilderness intervening 
between men'.- home.-. The blank areas are practically uninhabited, though crossed from 
time to time by the solitary hunter or prospector or wandering bands of nomads. 

2. A - lance at this map is enough to show how unevenly men are scattered 
over the earth. One continent has a good many people almost everywhere, another has 
larger spaces empty than are lived in by men. and two others have then northern and in- 
terior part- unoccupied while people are crowded into their southeastern and southern 
part-, in one case huddled together closer than anywhere else in the world. Why 
should the people of Asia prefer one corner of their continent so noticeably? Why 
are the Au-tralians so lew and why do they ding so to the southeastern part of their 
island continent, the corner that is farthest away from England? Yet the people are 
British and their trade is with England. Most of the steamers that go to Australia go 
from England through the Meditteranean, the Suez canal and the Red Sea and then 

.round the greater part of the continent of Australia to get at these people in the 
southeast. The fact is that the real Australia, the Australia of the Australian-, is just 
this southeastern part. Everybody knows of Europe as the home of many, many na- 
tions, and nations that have figured much in history, literature, art, and science. The 
map show- us that men have taken possession of more of that continent than of any 
other. Europe is the only continent with almost no desert spaces. Eighty-five per cent, 
of the surface of the continent is settled. The rocky rugged uplands of it- mountains 
and the frozen Arctic plain of northern Russia are the only part- of Europe that 

no inhabitants in permanent homes. This is the more noticeable in the light of 
the wide blank spaces on the map of each of the other continents, ranging from two and 
a half millions of square mile- in Australia to nearly eight millions in Asia, space 
enough for the whole continent of North America. There are not people enough in 
the whole world to settle Asia as closely as Europe is settled. 

3. The New World lands — the Americas, South 
Skttled Areas in Millions of , . ,. , , .. T , . 

c ., mmm Africa and Australia — look verv different on this 

Square Miles. 

Inhabited. Empty, population-map from the < >ld World lands. Why 

Asia 9 8 are they so thinly settled? Is it because they are 

N. America 3 IR . W mcre ] y because men have been going to them 

Q A 1 

from populous Europe only for a few centuries? 
Australia l /i 2 l /i ,,,,,, i • ., ■ i. i .l 

Africa. 9j4 2 Probably there is something in this. It may be that 

Europe J Y* some day there will be as many people in these lands 

•i similar areas in the old world. But we must 
not form hasty conclusions. Some of the newer 



28 22Y A 



4 



parts of Europe are more densely settled than old '".recce. Ruin- found in central 



Asia and parts of Arabia prove that those places have been known to men for a very 
long time and still they are very sparsely settled. Mesopotamia and most of North 
Africa have had time and history enough. Think of Egypt and Babylon and Persia and 
Syria and Phoenicia. Yet how thinly peopled today! In general it is the lands about 
the Baltic and the North Sea, new lands all in European history, that far excel in density 
the historic shores of the Mediterranean. Italy is only an apparent exception to this 
statement. It is true that the only North Sea countries that have a denser population 
are Britain, Holland and Belgium, but it is to geographic conditions that she owes this, 
geographic conditons that she shares with northern Europe, and of which other Med- 
iterranean countries are deprived. The chief of these is a more abundant rainfall, more 
evenly distributed throughout the year. 

4. There will be changes in the distribution of population in the new world as time 
goes on. There will be more people there, some of the thinly settled places will fill up 
and perhaps some regions will have fewer people than to-day. The state of Iowa, for 
instance, had fewer inhabitants in 1910 than in 1900. This will come about as people 
come to know better what parts of the new world are suitable for settlement, and as 
means of communication make remote places more accessible. If we knew to-day all 
about the resources of every part of the world, we should know its geography. That is 
precisely what geography is concerned with. Of course no one does know fully, but we 
get much light in trying to see why men have thriven and multiplied so much more in 
some places than in others. 

5. Europe is more thoroughly peopled than any other continent because millions 
of vigorous, restless men have wandered over it for thirty centuries, looking for homes, 
and finding them everywhere. They have proven it a good place to live in by living 
there, as men have not been able to live in the whole area of any other continent. In 
Asia men live mostly in the southeast because they have found that they could not live 
in other parts. They have tried it but did not thrive there. In the central deserts old 
settlements have long since died out and in the cold north only a few very rugged indi- 
viduals can keep alive. Children rarely grow up, population does not increase and it 
does not seem as if more than a few wandering hunters can ever make their homes there 
with climatic conditions as they are. If we can make out just why men thrive 
in one place and perish in another we shall be learning geography. The question that 
interests us always will be what is the fitness or unfitness of this place for man? Al- 
though America has been known only four centuries, there has been some selecting of 
the better places, some leaving of those first reached. Florida has been known longer 
than Michigan, but is not so thickly peopled. Nova Scotia and New Brunswick have 
been known longer, and are nearer Europe than Ontario, but they are much less popu- 
lous. We shall see that Ontario is better fitted for men, and we shall not know its 
geography until we know in just what respects it is fitter. In the new world the study 
of the country and the seeking out of resources has been very imperfectly done as yet, 
partly because we have not had time to do it and partly because we have got along so 
very comfortably by settling down in the first places we have come to that we have 
not had very much occasion to hunt for better ones. There are few people in the new 
world countries as yet and there is much land. It is for that reason that people in the 
new world are richer than in the older countries. Land is abundant and cheap and 



everywhere in the new world people have paid more attention to getting more land 
than to finding better land. 

6. In North America why are men so fond of the southeast and the Pacific coast? 
A glance at the rainfall map on page 13 shows how much it is like the population map. 
The rains seem to have a good deal to say as to where men shall live. When we call 
rainy days bad weather we are not thinking very much of our words. It would be the 
worst possible weather for us if we had no rainy days at all. In our continent the hun- 
dredth meridian sharply separates the arid west from the rainy east, everywhere north 
of the 30th parallel. The population map shows that the rainy east has a thin or mod- 
erate population, while the arid west is mostly scantily peopled. The rainfall data of 
these maps are the averages of many years. About 1890 there were several unusually 
rainy years and many people settled in western Kansas, thinking they were going to 
have rain enough there to raise crops, but the dry years came again and they had to 
abandon their farms. Less than twenty inches of rainfall in an average year appears 
to be insufficient for farming without irrigation. But while it seems desirable to have 
from 20 to 40 inches of rain a year, there is no increase of population where the rain in- 
creases to 40 or 80 inches. Alabama, Georgia, and Mississippi have more rainfall than 
Ohio, Indiana, and Illinois, but fewer people. 

7. The small empty spaces in Florida and Central America are not due to defect of 
rain. The very densely settled areas are not found occurring with very heavy rainfall. 
It is doubtful if man's prosperity is favored at all by more than 40 or 50 inches of rain. 
For these reasons we shall call rainfall less than twenty inches a year scanty, over twenty 
sufficient, over forty abundant, and over eighty excessive. For the rest, the conditions of 
the areas of dense population are pretty strongly contrasted. Man lives easily amid 
the exuberance of the tropics, in a fruitful land with a climate that imposes on man 
little need of shelter and clothing. The area of very dense population toward New Eng- 
on the other hand is in that belt of energetic American life between Baltimore and 
Boston in which resides so much of American culture, thrift and business ; where are 
so many large cities, so many great universities, so many associations with great men 
and great deeds in the history of the United States. South of the thirtieth parallel the 
rain falls from the Atlantic to the Pacific and men have no such east and west division 
as in Canada and the United States. The islands of rainfall that accompany the chief 
mountain ranges of the western plateaus are matched by islands of population, which 
stream even beyond the rainbelts along the river valleys that lead flood waters out into 
arid country, and make agriculture possible with irrigation. Canada is seen to be large- 
ly rainless and empty. 

8. Labrador is apparently well watered enough for occupation but there is little 
soil on its wilderness of rocks, as in most of the country north of the St. Lawrence and 
the line of Great Lakes between Lake Ontario and the mouth of the Mackenzie river. 
So along the Pacific coast of Canada and Alaska there is rain enough. Overmuch 
mountain and bare rock deter man from settlement. Norway, which has a similar posi- 
tion in Europe, has 96 per cent of her surface uninhabitable mountains. That is the 
meaning of the white places in Scandinavia in Figure 6. The picture from the west of 
Norway printed here shows how scarce the soil is in many parts of that country. So 



with abundant rains, Norway has but 18 people to the square mile in a continent where 
the average is a hundred. Yet even so moderate a peopling as Norway's — it would cor- 




Photo by Mark Jefferson. 
Fig. 1. The Scant Soil of Norway. 

respond to the dots of our diagram — has been the result of a thousand years of national 
life, during which the Norwegians have been searching out and utilizing every nook and 
corner of the country that can be used. 




Fig. 2. Uninhabited Switzerland. 

9. Switzerland shows the same thing with a history reaching back of the Christian 
Era. The diagram printed here shows very plainly how the Swiss people have tilled 
every scrap of usable land in their country. Where the diagram is black no people 



live, so the white places are the homes of men. We see that most of the Swiss are 
massed in what they call the Central Plateau, between the low Jura Mountains on the 
west and northwest and the lofty Alps in the southeast. The threads of white in the 
southern black masses are the narrow valley floors among the lofty Alps. The few black 
areas in the Jura Mountains of the north show how much rarer is really rugged and in- 
accessible ground in those more gentle mountains, where men live not only in the broad 
valleys but often on the gentle slopes and rounded summits. 

The mountains of Alaska may some day have such threads of population along their 
broader valley floors, but as yet they have no inhabitants. In the eastern United 
States we see on Figure 5 how the population thins out at the Ozarks in southern Mis- 
souri and in the Appalachian ridges further east. 

10. But all these are regions of abundant rainfall and there it is always noticed 
that the rugged, rocky slopes lack soil to support life. Such mountains repel men ; in arid 
countries mountains attract. In the western United States the cooling lift they give the 
winds brings very welcome rain. There every mountain is a green place, wooded and 
grassed, an island in the desert expanse. Men live there of necessity, not on the moun- 
tains, that men rarely do, but in the valleys between, and therefore always in limited 
numbers. The Rocky Mountain valleys support the people of the western States, but 
their population will never be dense. For however densely the valleys are settled there 
will always be useless land above. The dense population about Mexico City occupies a 
basin with rather less than twenty inches of rain, but easily watered from the surround- 
ing heights. 

11. Swamps and undrained regions, too, are difficult to use for homes and we see 
the population thin for this reason in the swamps along the Mississippi in Arkansas 
and Louisiana. Here is too much water, just as in the Everglades at the southern 
tip of Florida. 

When the swamps occur in very warm countries, like Central America and Brazil, 
plants may thrive so much better than men that only highlands are inhabited. It is not 
exactly correct to regard this as due to the heat, for the tropics are not so much regions 
of great heat as regions of continuous warmth. Greater heats, occur at the outer borders 
of the torrid zone than within it, but the lack of winter makes the warmth enervating and 
is remarkably favorable to vegetation. 

12. Men seek the heights in the tropic regions not directly because of the heat be- 
low, but rather because of the overwhelming luxuriance of the vegetation and the preva- 
lence of human ailments in the combination of heat and reeking dampness on the low- 
lands. To clear away the forest is a heavy undertaking even in our northern open 
woods. The opening up of Michigan was not to be compared for rapidity with that 
of the prairie states where the land was ready for the plow when the owner came to 
it. In the wet regions of the tropics the forests are inconceivably dense. To leave the 
trail is not merely difficult, it is sheer impossibility. Plants grow, not merely on the 
ground but on each other, until the whole space between the tree top and the ground 
is filled with a mat of interlacing growths. To make a clearing in such a tangle is a 
huge labor, to maintain it an endless one. Kipling's "Letting in the Jungle" well con- 
veys the idea of vegetation fairly obliterating a village. Perhaps the day will come when 




Photo by Mark Jefferson. 
Fig. 3. In the Woods on Mt. Misery, St. Kitts 

these forests must be tamed, but in America four centuries of Latin dominion has made 
no impression on them. Dominica in the West Indies is as impassable off the narrow 
road as when Columbus gave it a name. 

13. It cannot be accident that the peopling of Australia, South Africa and Mada- 
gascar is all to the east (see p. 14). Let us see therefore what peculiarity each of these has 
in its eastern parts. Each (see p. 16) has abundant rain on the east, steadily diminish- 
ing to scanty on the west. A glance at some political map of South Africa is instructive. 
On the west, reaching from the Atlantic more than half-way across the continent, 
are the great deserts of German SouthwestAfrica and Bechuanaland, then succeed for 
another considerable distance the semi-arid uplands of the Boer country further east, 
now Orange river and Transvaal colonies, and then, under the rugged slopes of the 
Drakensberg, by which the plateau breaks down on the east, the well-watered gardens 
of Natal. This thrice repeated group of features is a proper characteristic of an upland 
on which blow winds from an ocean to the southeast. It is not by chance that our 
people thin out so suddenly at the hundredth meridian, that the Pacific coasts of America 
are populated for thirty degrees on each side of the equator, then desert for the next ten 
degrees toward the poles in each hemisphere, thence peopled again beyond the forties. 
Surely the great things in geography are the agencies that have governed such a distri- 
bution of mankind. 



14. Upon careful examination of data 
woild, at least as far as broader features go, 
population group is broad soil-covered plai 
rainfall on these plains ; and the third, a tem- 
steadily warm as to enervate men and to pro 
rather than his servant. History reveals 
and more firmly and growing more and more 
new world has many a hint of similar tenden 



that are now fairly obtainable for the whole 
it appears that the first requisite for a great 
ns for their homes ; the second, sufficient 
perature neither too low for plants nor so 
voke vegetation to become man's oppressor 
man in the old world settling down more 
prosperous under these conditions. The 
cies. 



Iii the matter of rainfall Europe is singu 
than any other continent. Only the Spanish 
east Russia are limited in population from 
population leans so decidedly westward as 
sula is so close a reflection of its rainfall and 
rain are very small. 

So much of Australia is arid that only 
15. The distribution of people in 
densest population is rather over twenty- 
than the average density of the United 
are at once seen to lie always within 400 mil 
through the center of the continent would 
all the patches on the coast ; another to the 
near it. What determines this arrangement 
South America, though endowed with two 
leaves the greatest of these solitary and de 



larly happy. She suffers less from drought 
interior and southeast, and the steppes of 
this cause. Thus it happens that Russia's 
the map shows and that of the Iberian penin- 
therefore marginal. Its areas of excessive 

its eastern border can ever become populous. 
South America is somewhat peculiar. The 
six to a square mile, that is, a little more 
States. The patches of moderate population 
es of the sea. A northeast southwest line 
have a region to the southeast with almost 
northwest with none at the coast, but all 
? The mountains of the continent ; for 
of the greatest river systems of the world, 
serted and finds its mountains all-determin- 




Photo by Isaiah Bowman. 

Fig. 4. Cuzco in a High Valley in the Andes, 11,000 feet above Sea 



ing for the home of the nations. A glance 
that the populations of the northwest lie 
the thin peopling, indicated by the dots, obse 
of Capricorn. In Peru and Venezuela the 
in Columbia and Ecuador the transition is 
chains to thin at the coast and scanty on the 
16. The vast basin of the Amazon is 
people gathered along its eastern border, wh 
drawn away from the coast as on the Pacific 



at the map showing relief reveals the fact 
along the high valleys of the Andes, and that 
rves a similar behavior down to the tropic 
moderate population reaches the coast, while 

from moderate along the central Andean 

plains of the Amazon. 

seen to be all but deserted. Brazil has its 
ere it, too, is high, but the people have not 
Tropical South America has its people in 



the five mountain republics of the northwest — Venezuela, Colombia, Ecuador, Peru and 
Bolivia, and on the elevated eastern sea border in Brazil. The Amazon basin is a 
great hinterland on which all have claims, for the most part ill-defined or in dispute, 
but in which none have any significant number of citizens. It is in complete possession 
of aboriginal savages ; apart from isolated trading posts along the water. The equa- 
torial position, of course, is the cause. The dominant races seek the mountains to es- 
cape from the heat and moisture of the lowlands. The tropical Andes are the great 
rain producers of their continent in the cooling lift they give to the trade winds that 
blow from the Atlantic against their eastern slope, but their upper valleys are drier and 
are the truly temperate regions of the world. North of the twentieth parallel South 
America hardly knows greater differences between summer and winter temperatures 
than five or ten degrees. A lowland heat of 75 to 85 degrees proves very favorable to 
rubber, sugar cane, coffee and cocoa, but man ever since Inca days has preferred the 
drier, cooler mountains, always with the same narrow range. In the Andean republics 
the denser populations live where the thermometer ranges mostly between 50 and 60 
degrees or 55 and 65 degrees. 

17. South of the tropic the Andes serve to part men as well as the waters. The 
high valleys there are too bleak for permanent homes. There the Andes are a wall, a 
boundary. They are not essentially in Chile and the Argentine, but east of Chile and 
west of the Argentine Republic, a relation entirely different from that which prevails 
further north. The lowlands in the south have distinct summers and winters, hot and 
cool respectively. They are somewhat short of moisture, notably in the western Argen- 
tine plains, under the wind shadow of the Andes, for in this region of westerly winds the 
rains come from the Pacific or from disturbances that sweep eastward across the con- 
tinent. The plains here narrow in Chile, broad in the Argentine, are the home of pros- 
pering, thriving men, of communities that are taking part in modern life, with schools, 
railroads and active commerce, that puts them in contact with the other active people of 
the earth. 

18. There are not very many people in the world in comparison with its area. 
Texas would hold them all and give each man, woman and child a square seventy 
feet on each edge. They could stand much closer than that. Two thousand people can 
stand in a mile-long line very easily. They will have two and two-thirds feet between the 
centers of their bodies. A square mile so covered would have four millions on it, and the 
whole sixteen hundred millions of the world's people could stand in the little state of 
Rhode Island, and have abundant room to spare. But standing room is a very different 
thing from living room or "Sustenance Space," the area from which a man can draw his 
food or clothing. This varies greatly with the man's occupation, being very large for 
hunters and fishers, smaller for grazing nomads and lumbermen ; smaller still for agri- 
culturists. Thus it happens that there is a close relation between density of population 
and the occupations widely prevalent through a region. Generally these relations hold 
over the world except in India, China and Japan. Thus hunting and fishing may sup- 
port from two to eight people per square mile and they must of course be savages or 
barbarians, lacking as they do agriculture and the manufacturing arts. Grazing and 
lumbering may prevail with densities of 8 to 26 people. So all four of these occupa- 
tions are likely to occur in one part or another of the dotted areas of the map (Figure 5, 



see numbers on the Legend.) The student should check this up somewhat for himself 
by examining regions where he knows that lumbering, for instance, is general to see 
what the map indication is there. 

19. For agriculture, predominant where the population densities are from 26 to 
250, we distinguish two types. These might be called large farm and small farm agricul- 
ture, but better names are extensive and intensive agriculture, putting the- emphasis on 
the degree of thoroughness with which the ground is worked. The extensive or large 
farm agriculture characterizes regions where the density of population is from 26 to 125 
persons to the square mile. This is typical of southern Michigan. Here the farm house 
is apt to have four indwellers, and the numbers allow from 6 to 31 such farms in a square 
mile. Each farm must run therefore from 106 to 20 acres in size ; as a matter of fact we 
know they are mostly of forty, rarely of eighty acres. In the same way we may estimate 
that the intensive farming prevalent with population densities of 126 to 250 people to 
the square mile implies farms of ten or twenty acres. But they will be more thoroughly 
tilled and will yield much larger crops for the same area. Note the following figures 
from the 1909 Year Book of the U. S. Department of Agriculture. They are averages 
for the twenty years 1889 — 1908 of the yields of five important crops in bushels per acre 
for United States (extensive), and Germany and United Kingdom (intensive) : 





U. S. 


Germany 


U. Kingdom 


Potatoes 


90 


197 


186 


Wheat 


14 


29 


33 


Oats 


29 


SO 


45 


Barley 


26 


34 


35 


Rye 


16 


25 


27 (Ireland) 



It must not be supposed that extensive agriculture is bad agriculture. The table 
shows a German acre of land yielding about as much as two of ours. It involves more 
than twice as much labor though, each added bushel of yield costing a greater and greater 
increase of labor. Where land is cheap and labor dear, as with us, extensive farming is 
appropriate. Two-thirds of our farms are of more than 50 acres and of Germany's four- 
fifths are of less than 25 acres. 

20. For densities of population above 250 per square mile the predominant pur- 
suits are the manufacturing industries except in eastern Asia, where an agriculture so 
intense prevails that there is nothing like it elsewhere, with the population running to 
1000 and 2000 to the mile. 

Thet densent type of population, the world over is the city, made up wholly of men's 
dwelling places and working places at other than farm or field labor. The houses are 
many stories high and close together so as to wall in the street on either hand. Every- 
thing is planned for many people : streets paved for much traffic, stores for many buy- 
ers, banks for many peoples' deposits and loans, hotels for many visitors, warehouses 
for the storage of much goods, factories for making enormous output of wares, vehicles 
for the transportation of many people, and lights and policemen to guard against the 
many evil persons in so great a crowd. Ten thousand people to the square mile may be 
taken to signify a population so dense as to show all this. If parts of many incorpor- 
ated cities have less it means only that they have their suburban and even country parts 



10 

within the charter limits. In the outer parts of Chicago are farms and although this is 
politically city, it is really country after all. 

21. Distribution of Population in North America. Fig. 5 
Scale of Map : 942 miles to an inch. 

1. What one word best describes the density of population of North America 
north of the 50th parallel? 2. Has Canada more thin population north of 50° or scanty 
south of it? 3. In wbat states does a very dense population occur? 4. Name seven 
regions of dense population. 5. About what proportion of the United States is moder- 
ately peopled? Where? 6. How do the scanty and thin grades of population com- 
pare in area west of the 100th meridian? 7. Compare the density of population in the 
United States east and west of the 100th meridian ? 8. Explain (7) by Rainfall map. 

9. Describe and explain the density of population of Florida. 10. What is the principal 
grade of population south of the 30th parallel? 11. Why is there not the same differ- 
ence at the 100th meridian as in the United States? (See Rain map.) 12. Describe 
the east and west arrangement of grades of density of population in Central America 
and explain it. 13. What style of agriculture appears to be most prevalent in North 
America? 14. Describe the density of population along the Pacific coast from Vancou- 
ver Island to Lower California. 15. Explain it. 16. In general how well are the 
West Indies settled? 17. Why is northern Mexico so thinly peopled? 18. In what 
river valley do the people of Canada mostly live? Why? 19. What are the main agri- 
cultural regions of the United States? 20. What appear to be the occupations of 
northern and southern Michigan? 21. W hat five states have the largest area of scanty 
population ? 22. What five are the most uniformly moderately peopled ? 

22. Distribution of Population in Europe. Fig. 6 
Scale of Map: 508 miles to an inch. 

1. Name 5 countries with broad regions of very dense population. 2. Name 7 
countries where scanty population occurs. 3. What countries have large regions of 
thin population? 4. Describe the largest area of very dense population in Europe. Tell 
its shape, direction, length and width. 5. What five countries have spots of very dense 
population ? 6. What grade of population is most widespread about the shores of the 
Baltic Sea? 7. Locate the three population-types of the Baltic. What is the grade of 
population at its entrance? 8. Describe the density of population about the North Sea. 
What may be called its entrance ? 9. Describe the distribution of population in Italy. 

10. Describe the distribution in the Iberian peninsula. 11. Is there more of the dense or 
the moderate population on the shore of the Mediterranean and Black Seas? 12. What 
six countries have mostly the dense and very dense grades of population? 13. What is 
the most striking contrast between the location of the more densely settled regions in 
Great Britain and the Iberian peninsula? 14. Compare the density of population in 
eastern and western Europe. 15. Compare the population-densities along the 40th and 
50th parallels. (Figure 8 has the parallels numbered). 16. In what three countries 
do the population densities accord best with the data of the rainfall map? 17. About 
what point is Scandinavian life centered? 18. What sort of agriculture prevails in 
Italy? 19. What appear from the map to be the chief occupations in England? In 
northwest Scotland? 20. What five mountain ranges show plainly on the population 
map? 21. How do they show? 



11 




Fig. 5 



12 




13 




Fig. 7 



30 20 10 10 20 30 40 50 60 70 




Fig. 8 



14 




Fig. 9 

The population densities given are minimum values : very dense population being over 
250 per square mile and so on. The scanty population is less than 2J/2 people per square mile. 



15 




Fig. 10 

The population densities given are minimum values : very dense population being over 
250 per square mile, and so on. The scanty population is less than 2 l /> per square mile. 



16 

23. Distribution of Population in Asia. Fig. 9 

1. Name five groups of very dense population. 2. Locate and describe five areas 
of scanty population. 3. What American population-group corresponds in its position 
in its continent to that of China? 4. What ones to Asia Minor and Palestine? 5. De- 
scribe the distribution of population in Japan, India and China. 6. Compare the distri- 
bution of people and rainfall in China. (See Fig. 11.) 7. What grade of population 
occurs in the regions of excessive rain in India? Is that also true in other continents? 
8. In general why are the inhabited parts of Asia in the south and east? 9. Judging 
by density of population where is grazing most carried on? 

24. Distribution of Population in Africa. Fig. 9 

1. Describe the areas of scanty population. 2. What does the map of annual 
rainfall show there? 3. Where is the most densely settled part of the continent? 
4. Has it rain? How do the people manage to live there? 5. Why is Madagascar most 
populous in the east? 6. In general how well do the rain and population maps of 
Africa correspond? 7. To judge by density of population what are the main occupa- 
tions in Africa? 8. In general how is Africa settled? 9. Why has Morocco less popula- 
tion than Algeria? 10. Why has Uganda more population than British East Africa? 

25. Distribution of Population in South America. Fig. 10 

1. How wide is South America's strip of thin-to-moderate population? (The 
spaces between parallels in all parts of the maps are about 700 miles.) 2. In what 
portion of the continent is this strip? 3. What is its relation to the region of excess- 
ive rainfall? 4. Is this relation found anywhere else in the world? 5. In general 
what grade of rainfall is most often associated with considerable population? 6. What 
countries in South America have strips of moderate population on the coast? 7. What 
countries have moderate population in the mountains? 8. What countries have but 
two grades of population-density? 

26. Distribution of People in Australia. Fig. 9 and Fig. 10 

1. What fraction of Australia has scanty population? 2. About how many square 
miles of inhabited area has Australia? (See areas in the margin of the northern hemis- 
phere of the rainfall maps.) 3. In what respects does the distribution of population 
fail to agree with the rainfall map? 4. Explain the grade of population of northern 
Australia. What are the probable occupations of Australia's people? 

27. Annual Rainfall, North America. Fig. 7. 

1. What parts of the map show rain where no men live? 2. Why is this? 3. 
What meridian is a rainfall boundary in the United States? 4. Describe the rainfall 
of Canada. 5. Describe that of Mexico. 6. What is the shape of the scanty rain 
area ? 7. What percentage of the total areaof the continent is made up by areas with 
more than scanty rainfall? 

28. Annual Rainfall, Europe. Fig. 8 

1. Is there any region of sufficient annual rain where the population is scanty? 
2. About what grade of population corresponds to the large area of scanty rain? 3. What 
grade of rainfall prevails in the parts of Europe most densely populated? 4. Compare 



17 

the distribution of rainfall in the Scandinavian and Iberian peninsulas. 5. Does Eu- 
rope's abundant rainfall mostly correspond with the denser population? 6. Which is 
rainier, east or west Europe? 7. Which more populous? 8. What percentage of 
Europe has sufficient and abundant rain? 

29. Annual Rainfall, Asia. Fig. 11. 
1. Where is there excessive rain? 2. How much of Asia is dry? Where? 3. Lo- 
cate the sufficient rains. 4. Describe the distribution of rainfall in India. 5. How well 
does it agree with the distribution of people ? 6. Explain the distribution of population 
in connection with rainfall in the northernmost of the Philippine Islands (Luzon). 
7. Compare the rainfall and population of eastern and western Turkey. 8. Compare the 
rainfall and population densities of the East Indies in detail. 

30. Annual Rainfall, Africa. Fig. 11 

1. What percentage of Africa is dry? 2. Compare it with Europe in this respect. 
3. Where is Africa's excessive rain ? 4. Compare the distribution of rainfall in north- 
ernmost and southernmost Africa with that of people. 5. Does Africa anywhere show 
denser population where the rainfall is excessive? 6. Illustrate. 

31. Annual Rainfall, South America. Fig. 12 

1. Local areas of excessive rain. 2. How much of the continent is dry? 3. De- 
scribe the larger area of scanty rain. 4. What is the population grade along it? 5. 
How does South America compare with other continents in the general supply of rain- 
fall ? 6. What four countries have each four grades of rainfall ? 7. Describe the rain- 
fall of the Argentine Republic and Chile. 

32. Annual Rainfall, Australia. Figs. 11 and 12 

1. What proportion of Australia is dry? Where? 2. Where are the excessive 
rains? 3. How does Australia compare with other continents in raininess? 4. Aus- 
tralia and the United States have about the same area ; how do their rainy areas com- 
pare? 5. Which is rainier: New Zealand, Tasmania or Victoria? 

The student who has worked his way to this point will see the great control over 
man and his occupation that is exercised by rainfall. We shall now set forth the chief 
principles on which the distribution of rain depends. This involves a brief study of cli- 
mate. 



18 



ANNUAL RAINFALL OF THE 




Fig. 11 



SHADE 


RAINFALL 


Black 


Excessive 


Ruled lines 


Abundant 


Dots 


Sufficient 


Blank 


Scanty 



LEGEND 

DETAILS 
An annual rainfall, including melted snow, of over 80 inches. 
An annual fall of from 40 to 80 inches. 
An annual fall of from 20 to 40 inches. 
Less than twenty inches in the year. 



19 



WORLD (INCLUDES MELTED SNOW) 




Fig. 12 



After Herbertson. 

In the blank areas agriculture is hardly possible without irrigation. Within them lie all the world's 
deserts. 



20 

CLIMATE 

33. We shall get no clear idea of the climate of distant lands unless we know 
something about our own. We shall find no difficulty in picturing in our minds a snow- 
storm in Russia or a thunderstorm in Havana, for we are pretty familiar with others 
much like them at home. To get an idea of the dust storms of the desert is not so easy, 
but if we observe carefully the dusty squall that often precedes our summer thunder- 
storms and think of them lasting much longer, with the wind sweeping over plains of 
bare earth and sand, we may build up some notion of the thing, especially if we will 
further read good accounts by eyewitnesses. Successful imagining must have a basis of 
known fact for comparison or contrast. To grasp the important idea that the tropics are 
monotonously warm, important because the inhabitants of those regions are not men of 
famous deeds, as if some stimulus for ambition were 'lacking there — it will help wonder- 
fully to observe with some closeness how incessantly our weather goes from extreme to 
extreme. If the mind then attempts to conceive a continued warm spell, varied only by 
the addition of months of wet — not passing showers — and followed by other months of 
steady drought, one realizes something of the debilitating effect of tropical climates, and 
perceives perhaps the better the stimulus we are under from the great weather changes of 
our miscalled Temperate Zone. 

The local weather map is therefore the appropriate material for the study of climate. 
By its aid we may extend our direct observations to much of North America. 

34. Climate and weather reside in the lower air. Events above are of great im- 
portance, but the region of study is the lower air which we breathe, in which our bodies 
are constantly bathed, at the bottom of the ocean of air. 

The conditions of the lower air that concern us are chiefly: TEMPERATURE, 
PRESSURE (much air or little air), MOTION (winds), and the PRESENCE AND 
CONDITION OF WATER (rain, clouds.dew and frost). 

Temperature of the Lower Air 

35. You will henceforth observe each morning at as early an hour as you are in the 
habit of going out of doors, how the temperature compares with that of the day before. 
It should not be supposed that the reading of the thermometer replaces this exercise for 
the student. It is perfectly possible to read the thermometer and record its indication 
in the book without ever thinking what it means. It is desired that the student come to 
class with a mind active with regard to the weather. The daily consideration of the 
question whether it is warmer, or cooler than the day before or whether the temperature 
is not perceptibly different, will be found useful. A sufficient record is one of the words, 
"warmer," "colder," or "stationary." Any doubt is to be covered by the use of the word 
"stationary." It will appear very soon that the characteristic of our temperature is 
change — change through the day, change through the year; and change from day to 
day, apparently regardless of seasons. In what follows we look for the causes of this 
changeability. 

EXERCISE 1.— Temperature of Ground and Air. 

36. On a cloudless day take the temperature of some dirt that has been dried and 
exposed to sun and air for some time. It should be set out early in the morning on the 



21 



ground, a little away from any building in such a place that the sun will get at it all day. 
If no such place is available put it in one place for the morning sun and in another for 
the afternoon. The thermometer should have a cylindrical bulb which is just covered 
by a thin film of dirt as the thermometer lies on the dirt in the pan. Dealers in physical 
instruments have a cheap German thermometer that is good enough for the purpose. If 
it can be done safely, it is well to leave the pan and thermometer out all night when 
there are no signs of rain.' A few night observations by the teacher and some of the more 
enterprising students will add to the interest. The thermometer in the dirt should not be 
touched but lie always undisturbed. Each student should make three readings of this 

thermometer, and another that hangs, shaded, in the 
air nearby, at intervals of not less than an hour and a 
half between the readings and note the results neatly 
on the table. 

If the dirt is kept dry the pan of dirt may be used 
to show insolation in winter as well as in summer, 
and on very cold days when there is snow on the 
ground the class will be much surprised to notice 
that a thermometer placed in a pan of snow with 
its bulb buried in snow registers temperatures so 
cold and yet so much above the temperature of the 
air. Thus, on Feb. 12, 1914, we found at Ypsilanti, 
at 7, 9, 11, 1, 2,3 and 5, the air had temperatures — 6.3 
— 0.5, 6> 11.5, 12.5, 10.5, 5, while the snow showed 
— 7, 5, 15, 27, 27, 21.5, 10. The day was clear and al- 
most without wind. 




37. To judge from your observations of the temperature of the dirt in the pan and 
of the air, which heats up more rapidly, ground or air? Does it also heat up in greater 
amount? Does either get as hot at one as at noon? Which cools off faster? How do 
our observations show this? How would the observations of a cloudy day differ from 
these in the day time? In the night? Try it. Can you tell why dew and frost are not 
formed on the ground on cloudy nights? 

From the readings of the thermometers gathered by all the class members and an- 
nounced in the class discussion, fill out the whole of your table. 



38. Physically the- heat of the air consists in the rapidity of the vibration of the par- 
ticles ; the faster they go the hotter the air. So, too, of the ground, its heat consists of 
the rapidity of the vibrations of its particles. Heat is communicated from one body to 
another in two ways, (1) by conduction, when the bodies are close together, (2) by radi- 
ation at all sorts of distances. It is believed that it travels not as heat but as vibrations 
of all pervading ether*, which occupies not merely space but extends through all gases 
and even other bodies. The insolation then comes to us from the sun as vibrations of 
the ether which do not much heat the air in passing through it. So the radiation from 
the earth into the upper air and space is by the same sort of vibrations of the ether, 
which do not materially warm the air in passing through. Conduction, on the other hand, 
is illustrated by the warming of the air from the ground on which it rests. The ground 
being warmer than the air, its particles are vibrating faster than are those of the air. They 



22 

are therefore supposed to hurry the adjacent air particles along in their swings until 
those too go more nearly at the same rate as the earth particles. Of course in doing this 
they lose some of their own speed and the result is a cooler earth as well as a warmer 
air. In usual language we say heat has been conducted from the ground to the air. 
And all the time that the lower air is being warmed by conduction heat is radiating away 
from the ground through it to be lost in space, without much effect on the air on the 
way. For conduction one body must be warmer than the other, but radiation goes on all 
the time from cold bodies as well as hot, though its amount is proportional to the 
temperature. A hot body radiates more heat than a cold one. And so summer and 
winter, day and night, in cold and heat alike, heat is radiating away from the earth, just 
as on all clear days insolation comes to the earth through warm air or cold. 

39. The effects of the sun's rays are different according to the thing they fall on. 
Clear air allows them to pass through with little effect on it, so that a good deal of inso- 
lation reaches the surface of the earth below. If this is land it heats up readily; if 
water, much less, since the rays pass through water somewhat as through air, although 
less freely. Anyone who has bathed on a sandy shore knows how strongly bits of stone 
or metal become heated in the sunshine, far more than water ever does. Shallow waters 
attain a more agreeable temperature than deeper water, because the rays are able to 
pass through and warm the bottom, which warms the water in turn. The waters of 
Lake Erie, which is shallow, become quite warm in summer, those of Lake Superior, 
which is deep, are always icy cold. The landsurfaces are thus seen to be most sensible to 
the sun's warming power. For one thing the effects on solids are confined to the surface 
layers. At a very moderate depth below the surface of rock or dirt exposed to the sun- 
light, no warming at all occurs. At a desert station in Turkestan, the mean temperature 
of the ground in the heat of the day, is 90°, but just before sunrise, 41°. Sixteen inches 
under ground the temperatures are 58.5° and 57.4°, respectively, almost a uniform temper- 
ature from day to night. Most of the heat is concentrated in the five or six inches of 
depth just below the surface. In water the penetration is far greater. Some lakes in 
the temperate zone are warmed by the sun's rays as much as forty feet below the sur- 
face. The effect is therefore distributed through a mass of water so thick that each com- 
ponent layer is but little warmed. Moreover, a great part of the effect of the sun's rays, 
on the water surface is used in evaporation, without causing any sensible rise in tem- 
perature. Finally, water is a very hard thing to warm. From all of these causes it re- 
sults that the ocean surface, or the surface of a deep lake is slow to warm and slow to 
cool. 

40. Clean air is so transparent to insolation, that at times when the sun is high, 
three-fourths of the sun's heating power may become effective on the ground after pass- 
ing through the whole depth of the air. Mainly, then, it is the dry land that is 
warmed by the sun. The most important point for the study of the weather is that the 
air is mostly warmed by the ground on which it rests and little by the rays of the sun 
that pass through it. The air temperatures never become so high as those of the 
ground. By what process does the ground warm the air (see 38) ? 

LODGE.— The ^ther of space. Nature, Jan. 14, 1909. p. 322. 



23 





Temperatures 


Hour 


Air Dirt 


8 


30 


22 


9 


35 


52 


10 


40 


66 


11 


45 


76 


Noon 


49 


80 


1 


52 


81 


2 


53 


74 


3 


52 


58 


4 


49 


42 


5 


45 


39 


6 


43 


37 


7 


41 


35 



February 22, 1916 the following temperatures 
were observed in the air and on the surface of a pan 
of dirt at Ypsilanti, Michigan. The day was clear 
till 3 :30, when clouds came up. There was very 
little wind. 

How much warmer did the ground get than the 
air? When did the ground reach its greatest heat? 
What was the range of temperature — the differ- 
ence between the least and greatest temperatures — 
that day in the air? On the surface of the ground? 
It will be noticed that neither ground nor air was 
warmest at noon. 



41. In general the heat received by the ground depends on the height of the sun 
in the sky. It is greater, therefore, at noon than in the morning, greater in summer than 
in winter, and greatest in the tropics where the sun at times stands overhead. Let the 
page of this book represent the surface of a town or city, as the book lies flat open on 
th table. In the torrid zone the sun shines down on it from above, and the bundle of 

rays that touch the page is as thick 
through as the page is wide. At Ypsi- 
lanti, however, the sun shines on the page 
from a point a little above the horizon, 
and a thin bundle, containing a few 
rays spreads over the same surface. 
Thus the thick bundle of tropical rays 
s s' (Fig. 13) renders much more heat 
to the surface in which A B is a line 
than the thin bundle of rays s" s'" ; 




Fig. 13 



although each bundle is just wide 
enough to shine on the whole width of 



A B. In the United States, of course, the sun is never overhead but its heating power 
is greater in proportion as it gets higher in the sky. 

42. Working against this warming by the sun is the radiation by which the earth 
is always giving up heat, even while the sun is shining down upon it ; most at the season 
when the earth is warm, but always in considerable amount. Whether the earth is 
gaining or losing heat at any moment, depends on the relation of this radiation to inso- 
lation, or solar warming. From the tables of temperature given, and from the January 
temperatures at Ypsilanti, we learn that the maximum or greatest heat does not occur 
until afternoon. 1. While the earth is warming which must always be greater, insola- 
tion or radiation ? 2. If it is warmer at one than at noon, is insolation or radiation 
greater between those hours? 3. When is insolation greatest? 4. What change is 
it undergoing from noon to one ? 5. How can a diminishing insolation still cause the 
earth to get warmer? (See 1). 6. What is the relation of insolation and radiation at 
the moment of greatest heat? 7. Before that moment? After? 8. Why is it not hot- 
test at noon? In par. 40 the ground was steadily gaining heat as the sun rose higher 
in the sky. If there was heat lost by radiation, it was less than was received from the 



24 

sun at the same time. At 1 p. m., the maximum temperature of 81° was attained. 
From that moment we must regard the loss by radiation as greater than the insolation, 
and the ground cooled off steadily. 

The same effect is observable in the air temperatures, and here the maximum comes 
still later. 

43. Only six miles above the surface of the earth the air stays about 55° below zero 
throughout the year, summer and winter alike, in sunshine or in darkness, in the temper- 
ate zone or over the equator. There are differences of temperature up there, it is true, 
but oh, so tiny ! The thermometer may rise in summer to 49° below zero and in winter 
drop to 63° below. Bright sunshine may give a temperature one degree higher than pre- 
vails by night, but we have learned beyond a doubt by sending up kites and balloons to 
which self-registering thermometers are attached, that the upper air is always bitterly 
cold, colder than many of us have ever had any experience of. As was said, it always 
stays about 55° below zero. 

44. When we feel the uncomfortable heat of the noonday sun in summer, we must 
not forget that it has come to us through this icy upper air, and that it was in that icy air 
the instant before it reached us. Light travels so fast that six miles is passed through 
in the tiniest fraction of a second. It is quite certain, therefore, that the sun's heat can 
pass through air without warming it very much. The air in which we live, the air next 
to the ground, is warmed almost entirely by the ground it rests on. For the sun's heat, 
that has so little effect on the air it passes through, heats the ground strongly, in sum- 
mer to 168° and 170°. The heated ground, in turn, is the source of the heat of the 
summer air. When we say it is hot in summer, the "it" we refer to is the lower air. Its 
highest temperatures are noticed near the ground. The temperature on a high tower is 
usually a degree or more colder than near the ground. 



45. In the city of Paris, France, there is a graceful steel tower nearly a thousand 
feet high, the Eiffel Tower, from the name of its constructor. Thermometers are installed 

at top and bottom of the tower and have been re- 
corded for many years. Here are some temperatures 
for a summer day: 

What was the range of temperature at the top of 
the tower? What in the air below? That is nearly 
twice as much below as above, though it was not 
what you and I should call a hot day. It was not 
hottest at noon but afternoon. At what hour? How 
much hotter below than above? 





Temperatures 




Air 


Air Dirt 


Hour 


it 1000' 


at base at base 





59° 


59° 


55° 


4 


56 


56 


54 


8 


58 


64 


82 


N 


64 


70.5 


97 


2 


65 


71 


98 


4 


65.5 


71 


91 


8 


62 


60 


57 


12 


59 


60 


52 



46. 



EXERCISE 2. 
Figure H is a curve constructed to show the temperatures of the surface of 



the ground near the base of the tower that day. The vertical lines represent hours of 
the day and the horizontal ones every tenth degree of temperature. On the first vertical 
line, which stands for zero hours (midnight), we have put a dot half way between the 50° 
and 60° horizontal lines to represent the 55° of the right hand column of the table, the 



25 




temperature of the surface of the ground at midnight. On the second (4 o'clock) line 
the dot was put a little below half way from 50 to 60 to represent the 54° of the table at 
4 o'clock, and so on through the day. Finally a smooth curve was drawn through all 
the points. You will notice that the temperature is given for 2 p. m. as well as for noon 
and 4. Draw curves for the air temperature at the base of the tower with red pencil, 
and for the air at the top in blue pencil on the same diagram, Figure 14. 



Diagram of the temperature of the 
ground in Paris through a summer 
day. On this same diagram each 
student is to place the temperature of 
the air at the foot of the Fiffel tower, 
red curve, and at the summit of the 
tower, blue curve. 



Fig. 14. 

Is it by day or by night. that the three curves differ most? How much hotter did 
the ground get than the air? Why was the lower air six degrees warmer than the upper 
air at 2 p. m.? 

EXERCISE 3.— Temperatures on Land and Lake. 

47. This table gives the temperature of the air 
about as it is near Gaylord and at a point over the 
middle of Lake Michigan west of Traverse City on 
a very hot still day in August and a very still cold 
one in February. Construct curves for each, calling 
one square vertically two degrees and horizontally 
one hour. 1. What was the range of temperature 
in Gaylord in summer? 2. How much in winter? 
3. What were the temperature ranges over the Lake? 4. Which place was warmer 
in summer? 5. Why? 6. Which was warmer in winter? 7. Why? (Probably 
Lake Michigan never freezes all across. This is the report of the masters of steam- 
ers which ferry freight trains across all winter from Ludington and Grand ' Haven. 
They sometimes encounter drifting ice-floes and much continuous ice near the Michigan 
shore). 8. Why did it never go much below 33° out over the Lake? 9. Is 33° cold 
weather or mild, as winter weather goes ? 10. Which probably has the milder winter, 
Traverse City or Gaylord ? 11. Why? 12. Why has Milwaukee greater cold in win- 
ter than Grand Haven? Note that our winds are usually from the west, that is more 
often than from any other direction. February 9, 1914 Milwaukee had four below 
when the air at Grand Haven was at ten above. The wind at Grand Haven was 





Gaylord 


Lake 


Hour 


Aug. 


Feb. 


Aug. Feib. 





67° 


—4° 




4 


64 


—7 


57 34 


8 


68 


—7 


60 35 


Noon 


n 


4 


62 36 


4 


81 


8 


62 36 


8 


72 


3 


60 34 


12 


69 


1 


59 33 



26 



blowing- twenty-five miles an hour from the west. The same morning Saginaw had six 
below and Saugeen ten above, and the wind at Saugeen was southwest thirty-five miles 
an hour. 13. Why was Saginaw colder than Grand Haven and why are Saginaw 
and Alpena not summer resorts? 14. Why are the summer resorts of Lake Michigan 
along the eastern shore? Name them. 

48. Over the ocean the air has a still smaller range of temperature. Half way 
from Newfoundland to Ireland the air in summer averages 60° and in winter 40°. The 
frequest west winds blow this mild ocean air, that is neither hot in summer nor cold 
in winter, over the western lands of Europe, giving them a mild climate, much less hot 
in summer and much less cold in winter, than in the same latitudes in eastern Europe 
or in eastern America. 

Labrador and Great Britain are in about the same latitude, but Labrador is bathed 
in land air by the same west winds that bathe Britain in air from the ocean. . So Labra- 
dor is hotter in summer and colder in winter. If there were warm water flowing along 
the coasts of Europe would it make the summers there cool? We have often been 
told of such warm water but an immense number of observations of the temperature 
of the water off the Irish west coast show that it does not exist. The variations are 
not great. The February temperatures of those waters is 50° and the August tempera- 
ture 60°. The winter temperature, 50°, is warm for winter, truly, and winds off it keep 
the winters very mild but it is cold water. Even the summer water at 60° cannot be 
called warm. 

EXERCISE 4. 

49. Draw four temperature curves from the data in the following table, which 
gives average hourly temperatures for summer and winter months at Ypsilanti and 
Cuzco. Put all four curves on a single diagram with one square of the quadrille paper 
vertically for 2° and one square horizontally for one hour. 1. Where is Cuzco? 2. In 

what latitude? 3. At what altitude. 4. Which 
place has the more temperate weather? 
5. How much warmer are summer days at 
Cuzco than winter ones? Cuzco has distinct 
wet and dry seasons, with 66 per cent, and 37 
per cent, respectively, of cloudy weather. Now 
clouds have two effects on the temperature. 
They (1) prevent the suns rays from reaching 
the ground, and (2) they prevent the earth's 
heat from radiating away. The 27th of Janu- 
ary, 1904, at Ypsilanti (see paragraph 53) was 
clear and the 22nd was cloudy. The 22nd 
shows both (1) and (2). 6. Do clouds lift 
or lower the day part of the curve? 7. How 
do they affect the night part? 8. How the 
daily range of temperature? 9. When has 
Cuzco less daily range? 10. When has Cuzco clouds and rain? 11. Is January or July 
summer at Cuzco? 12. Which curve should run among higher temperatures? 13. 
Which does run higher? Before considering the next question, construct a broken-line 





Cuzco 


Ypsilanti 


Jan. 


July 


Jan. 


July 





48 


38 


14 


65 


2 


47 


36 


14 


64 


• 4 


46 


35 


14 


62 


6 


46 


34 


14 


65 


8 


49 


41 


14 


68 


10 


55 


51 


17 


74 


N 


60 


57 


20 


77 


2 


59 


59 


21 


79 


4 


56 


56 


20 


77 


6 


54 


49 


18 


75 


8 


51 


44 


16 


72 


10 


49 


40 


15 


67 





48 


38 


14 


65 



27 

curve to represent the following temperatures at the hours of the table: — 45°, 43, 42, 41, 
48, 58, 65, 66, 63, 56, 51, 47, and 45. The curve may be put on the same diagram with the 
other two. It represents what the temperatures might be at Cuzco in January if the 
sky were cloudless. Clouds change this broken-line curve into the actual January 
curve. 14. Why do the January nights differ more from July nights than January 
days from July days? 

EXERCISE 5. 

50. It will help toward clear thought if, in speaking of this afternoon maximum of 
temperature, we refer its time, not to noon, but to the thing which fixes noon ; the sun's 
height in the sky. 

1. When in the day — in terms of the sun's height in the sky — is it hottest? AFTER 
THE MOMENT OF HIGHEST SUN. The sun is highest of all the year for us on 
June 21st, the summer soltice. 2. When in the year, in similar terms to those just 
suggested, is it hottest? Let us now construct annual temperature curves for Cuzco 
and Ypsilanti, counting one square of the quadrille paper vertically for a degree and two 
squares horizontally for a month. We shall use the mean or average temperature of the 
whole month and consider the date that of the middle of the month. 

3. At Ypsilanti at what date in the year is it hottest? 
4. At what date is the sun highest? 5. What is the time 
of greatest heat in terms of the time of high sun? The 
Cuzco curve is peculiar. 6. When does it appear to be 
hottest at Cuzco? Hottest must here be taken to mean 
hotter than just before and just after. In that sense could 
there be two hottest moments? 7. How often is the sun 
high at Cuzco? 8. At what seasons, as we call them? 
9. At that time at what point in the Cuzco sky is the 
sun? 10. When is it hottest at Cuzco, with respect to 
the high sun? 11. Why are not the two high moments 
six months apart? The sun crosses the Cuzco zenith on 
the 12th day of February and 30th of October. 

51. The student should now add to his daily weather record the direction of the 
wind and the force of the wind as expressed in the Hazen wind scale. 

Force of the Wind. 

— Calm. 1 — Moves leaves of trees. 2. — Moves branches. 3 — Sways branches, 
lifts dust. A — Sways trees, lifts twigs from ground. 5 — Breaks small branches. 6 — 
Destroys everything. Hurricane. 

52. The temperature of a day may be ascertained by averaging the observations 
of a thermometer read every hour, but so many readings are very troublesome to 
make. Where the expense of $25 does not prevent, an instrument like our thermo- 
graph gives good results with very moderate care. A much less expensive instrument 
($5), that is little trouble to use is the maximum and minimum thermometer, to be seen 
in our laboratory and explained at page 60 of Davis' Meteorology. By referring to the 
temperatures given in 53, we readily make out the relation of the half-sum of maximum 
and minimum temperatures to the mean of the twenty-four hourly observations. On 



Cuzco Ypsilanti 

January 51 5 24 5 

February 51 9 23 

March 52.2 32.6 

April 51.3 46 3 

May 49.6 56.8 

June 46 6 66 1 

July 45.0 69.8 

August 48.1 67.7 

September... 49.9 61.3 

October 512 49.4 

November 51.8 36.8 

December 51.2 27.1 



28 

January 1st, the minimum was 12°, maximum 24°, their half sum, 12+24-^-2=18. The 
mean of the twenty-four hour values is 19°. 1. On the second the half sum is 4° to a mean 
of 7°.3. 1. How is it on the third, fourth, fifth and sixth? 2. Make the same com- 
parison for the mean values at the bottom of the page in both 53 and 54. The two 
numbers are usually within a degree of each other. For very many places in the world 
this is our only means of getting the temperatures. Those for Ypsilanti in 49 result 
from 15 years of such observations. 



53, HOURLY TEMPERATURES AT YPSILANTI, MICHIGAN 

JANUARY, 1904 





MORNING 


AFTERNOON 




Jan. 


1| 2 | 3 


4 I 5| 6 


7 


1 8 


1 9 


1 io 


|11| N 


1 1 


21 


3 1 


4 I 


5 1 


6 I 


7 | 8 9 | 


10 


11 | Mt. 


Mean 


1 


23 


24 


24 


24 


22 


22 


21 


19 


18 


20 


21 


22 


22 


22 


22 


21 


17 


16 


16 


15 


13 


12 


12 


12 


19~ 1 


2 


12 


12 


11 


10 


10 


9 


8 


7 


7 


7 


7 


8 


9 


10 


10 


10 


10 


9 


8 


6 


2 





-2 


-4 


73 


3 


-4 


-6 


-7 


-7 


-8 


-9 


-8 


-7 


-5 





3 


5 


7 


9 


10 


10 


8 


7 


5 


5 


6 


6 


5 


5 


1.2 


4 


4 


2 


2 


1 





_<7 


-3 


-3 





4 


9 


11 


11 


10 


10 


10 


8 


7 


4 


2 


1 


*-l 


-2 


-4 


3.4 


5 


-6 


-6 


-6 


-7 


-7 


-6 


-4 


-1 


2 


6 


9 


11 


12 


18 


16 


14 


14 


14 


14 


13 


13 


16 


16 


14 


6.6 


6 


14 


12 


12 


13 


14 


16 


17 


19 


20 


22 


24 


24 


25 


28 


28 


27 


25 


24 


23 


22 


23 


24, 


24 


24 


21.0 


7 


24 


25 


25 


24 


24 


24 


21 


20 


20 


20 


21 


24 


24 


25 


26 


28 


29 


29 


29 


29 


31 


31 


31 


31 


25.6 


8 


32 


33 


34 


34 


34 


34 


35 


35 


34 


35 


35 


36 


36 


33 


33 


33 


32 


31 


31 


30 


29 


27 


26 


24 


32.3 


9 


24 


22 


22 


23 


22 


22 


21 


21 


22 


22 


23 


24 


24 


24 


24 


23 


22 


22 


22 


22 


22 


21 


20 


14 


22.0 


10 


12 


10 


6 


4 


4 


4 


6 


9 


11 


13 


16 


18 


19 


20 


20 


20 


20 


20 


20 


20 


20 


20 


20 


20 


14 7 


11 


20 


20 


19 


19 


18 


18 


17 


15 


13 


12 


14 


15 


17 


18 


17 


17 


17 


18 


18 


19 


19 


19 


20 


20 


17.5 


12 


19 


20 


20 


21 


21 


22 


22 


22 


22 


23 


24 


24 


25 


25 


25 


25 


25 


25 


25 


26 


26 


25 


24 


24 


23.3 


13 


20 


22 


24 


24 


25 


26 


26 


26 


26 


26 


26 


27 


27 


26 


25 


24 


23 


23 


24 


24 


24 


22 


22 


21 


24.3 


14 


23 


24 


24 


24 


23 


23 


20 


20 


20 


21 


22 


22 


22 


22 


23 


23 


22 


22 


22 


22 


21 


20 


20 


18 


21 8 


15 


18 


18 


19 


18 


16 


17 


18 


17 


18 


21 


23 


25 


25 


25 


24 


24 


24 


24 


23 


22 


22 


22 


22 


22 


21.1 


16 


22 


22 


23 


23 


23 


24 


27 


28 


30 


31 


31 


30 


27 


23 


22 


20 


19 


18 


16 


15 


14 


13 


12 


12 


21.9 


17 


10 


11 


12 


13 


13 


13 


12 


11 


11 


11 


11 


13 


14 


14 


14 


14 


12 


12 


12 


11 


10 


11 


10 


7 


11 8 


18 


6 


5 


4 


4 


4 


4 


4 


4 


4 


8 


10 


13 


13 


12 


11 


8 


7 


5 


4 


2 


2 


2 


3 


4 


60 


19 


4 


6 


7 


7 


7 


8 


8 


9 


10 


12 


14 


18 


21 


25 


28 


30 


32 


34 


35 


36 


36 


36 


36 


36 


20.6 


20 


36 


36 


36 


36 


36 


36 


36 


36 


36 


36 


37 


36 


36 


34 


34 


33 


32 


32 


32 


32 


32 


32 


32 


32 


34.4 


21 


32 


32 


32 


32 


32 


31 


30 


30 


31 


32 


32 


32 


32 


33 


33 


32 


32 


32 


32 


31 


31 


31 


30 


30 


31.5 


22 


31 


32 


32 


32 


34 


34 


34 


34 


33 


34 


34 


32 


32 


32 


32 


31 


30 


28 


28 


28 


28 


28 


28 


28 


31.2 


23 


28 


27 


26 


26 


26 


26 


26 


26 


27 


28 


28 


28 


28 


28 


26 


25 


22 


20 


17 


14 


11 


10 


10 


10 


22.6 


24 


6 


5 


4 


3 


1 





-1 


-1 





2 


4 


5 


5 


5 


5 


2 


-1 


-3 


-4 


-5 


-6 


-6 


-6 


-6 


0.3 


25 


-7 


-7 


-7 


-7 


-7 


-6 


-6 


-5 


-4 


-1 


2 


4 


7 


8 


7 


6 


6 


6 


5 


4 


4 


4 


4 


4 


0.6 


26 


4 


4 


4 


4 


5 


6 


6 


7 


8 


10 


10 


11 


12 


12 


14 


13 


11 


10 


9 


8 


9 


9 


7 


6 


8.3 


27 


6 


6 


6 


5 


4 


4 


3 








3 


6 


9 


10 


10 


10 


10 


8 


5 


3 


2 


1 








1 


4.7 


28 


3 


4 


4 


4 


4 


4 


4 


3 


5 


7 


10 


12 


14 


15 


17 


17 


15 


12 


9 


6 


5 


4 


5 


4 


7.8 


29 


4 


6 


6 


5 


5 


6 


6 


7 


10 


15 


17 


18 


20 


21 


21 


19 


16 


11 


12 


7 


1 


-1 


-2 


-2 


9.5 


30 


-2 


-2 


-1 


3 


5 


7 


9 


12 


17 


22 


25 


26 


28 


29 


27 


26 


26 


27 


27 


27 


28 


27 


26 


26 


18.5 


31 


25 
14.2 


25 

14.3 


24 

14.2 


25 
14.2 


26 
14.1 


26 

14 3 


26 

14.2 


28 
14.5 


28 

15:3 


28 
17.1 


28 
18.1 


28 
19.7 


27 


25 
20.7 


24 
20 6 


22 
19.9 


22 

18.8 


20 
18.1 


20 
17.5 


18 
16.5 


17 
16.0 


16 

15.4 


16 
15.1 


16 

14.5 


23.3 


Mean 


20.4 


16.6 



29 



Air Tends to Expand When Heated, and to Yield to Pressure When Cooled 

55. Why does air expand when heated? The particles of air are believed to be in 
rapid motion, vibrating in some way back and forth. The faster the vibration, the hot- 
ter the air. The particles are of course too small to see with the most powerful micro- 
scope ; the distances through which they move are doubtless also very small, and the 
speed of the motion very great, even for bodies at ordinary temperatures. This is 
our general conception of warm bodies. If the vibrations are more rapid when the 
air is warmer, to heat a mass of air is to set its particles vibrating faster, but it is also 
natural, therefore, to think of these particles as pounding on the walls that confine them, 
and demanding more space and taking it, if not resisted by a force too great. Similar- 
ly when air is cooled its particles are thought of as vibrating more slowly, and moving 
through smaller spaces. They may be supposed, therefore, to strike less vigorously 

54. HOURLY TEMPERATURES AT HAVANA, CUBA 

JANUARY, 1904 



| MORNING 


AFTERNOON 




Jan. 


1 I 2| 3 | 4| 5 | 6| 


7 | 8 | 9 | 10 | 11 | N 


1 | 2| 3 | 4 | 5 | 6 


7| 8| 9 | 10| 11 | Mt. 


Mean 


1 


64 


64 


63 


63 


63 


63 


62 


64 


67 


68 


70 


72 


73 


73 


73 


73 


72 


70 


69 


68 


67 


66 


65 


65 


67^4 


2 


64 


64 


63 


63 


63 


61 


61 


66 


70 


73 


75 


76 


76 


76 


77 


76 


74 


72 


71 


70 


69 


68 


67 


66 


69.2 


3 


64 


64 


64 


63 


62 


63 


64 


68 


73 


76 


78 


76 


76 


75 


75 


75 


75 


74 


74 


74 


72 


72 


72 


71 


70.8 


4 


71 


71 


70 


70 


70 


70 


71 


70 


71 


71 


71 


72 


72 


73 


73 


74 


72 


71 


71 


71 


71 


70 


69 


69 


71.0 


5 


70 


70 


70 


69 


68 


67 


67 


67 


68 


69 


70 


70 


70 


68 


67 


67 


67 


66 


65 


66 


66 


67 


66 


66 


67.8 


6 


65 


65 


66 


68 


68 


67 


67 


65 


68 


73 


74 


73 


73 


73 


73 


73 


72 


70 


68 


67 


66 


65 


64 


64 


68.6 


7 


63 


62 


62 


62 


61 


61 


61 


63 


67 


71 


72 


73 


74 


76 


77 


75 


74 


74 


73 


70 


69 


67 


67 


67 


68.4 


8 


67 


71 


71 


72 


72 


72 


71 


70 


70 


71 


71 


72 


69 


70 


70 


70 


70 


68 


68 


67 


67 


67 


66 


67 


69.5 


9 


66 


66 


65 


65 


64 


64 


64 


64 


66 


69 


70 


70 


72 


71 


70 


71 


70 


68 


67 


65 


64 


62 


61 


60 


66.4 


10 


60 


60 


60 


58 


57 


57 


58 


60 


64 


70 


73 


74 


75 


78 


77 


77 


77 


75 


74 


70 


70 


70 


70 


70 


68.1 


11 


68 


68 


69 


68 


68 


68 


68 


68 


72 


75 


77 


79 


81 


77 


78 


80 


79 


77 


74 


72 


71 


71 


71 


70 


72.9 


12 


70 


70 


69 


69 


69 


67 


67 


70 


74 


78 


80 


80 


79 


79 


78 


77 


77 


76 


74 


72 


71 


70 


69 


68 


73.0 


13 


67 


66 


65 


66 


65 


65 


65 


66 


68 


74 


76 


77 


78 


78 


78 


78 


77 


77 


74 


72 


71 


69 


69 


69 


71.2 


14 


69 


67 


66 


66 


66 


66 


66 


66 


67 


69 


68 


67 


66 


66 


65 


65 


64 


64 


63 


63 


62 


61 


61 


60 


65.1 


15 


60 


61 


61 


60 


61 


61 


61 


65 


66 


67 


68 


68 


69 


70 


70 


69 


69 


68 


66 


65 


64 


63 


60 


60 


64.7 


16 


59 


60 


60 


60 


60 


60 


61 


63 


67 


70 


70 


7a 


73 


73 


74 


74 


74 


72 


69 


68 


67 


66 


65 


64 


66.8 


17 


64 


64 


64 


63 


62 


62 


61 


62 


66 


73 


74 


73 


73 


74 


75 


74 


74 


73 


72 


71 


70 


68 


66 


65 


68.5 


18 


64 


63 


62 


61 


60 


60 


60 


63 


66 


71 


70 


73 


74 


74 


74 


74 


74 


72 


71 


71 


72 


71 


70 


68 


68 3 


19 


68 


67 


68 


68 


69 


69 


69 


71 


71 


74 


75 


74 


74 


74 


73 


73 


73 


72 


71 


71 


72 


70 


71 


70 


71.1 


20 


67 


68 


70 


69 


68 


67 


68 


68 


69 


72 


73 


74 


74 


75 


75 


74 


74 


72 


71 


70 


70 


69 


69 


68 


70 6 


21 


66 


65 


65 


66 


65 


63 


63 


64 


68 


71 


74 


76 


76 


78 


78 


78 


79 


78 


75 


74 


74 


71 


71 


68 


71.1 


22 


67 


67 


68 


66 


67 


66 


65 


70 


73 


74 


75 


78 


79 


80 


81 


80 


79 


77 


76 


75 


74 


74 


73 


74 


73.3 


23 


74 


73 


72 


71 


71 


71 


70 


71 


71 


71 


73 


75 


78 


79 


80 


80 


79 


78 


77 


76 


75 


74 


74 


73 


74.4 


24 


73 


73 


72 


72 


70 


70 


68 


66 


63 


64 


64 


64 


65 


63 


63 


62 


61 


63 


64 


65 


65 


66 


66 


66 


66 3 


25 


66 


67 


66 


66 


67 


69 


68 


68 


69 


70 


73 


74 


76 


76 


77 


77 


77 


76 


74 


74 


73 


72 


71 


70 


71.5 


26 


69 


69 


69 


69 


69 


68 


67 


70 


71 


74 


75 


79 


80 


78 


76 


73 


73 


72 


72 


70 


70 


70 


70 


69 


71 8 


27 


69 


69 


68 


67 


67 


66 


65 


66 


68 


74 


77 


76 


77 


77 


77 


76 


76 


77 


76 


75 


74 


72 


71 


71 


72.1 


28 


70 


68 


67 


68 


67 


67 


67 


68 


69 


73 


74 


76 


78 


79 


78 


79 


78 


77 


75 


74 


73 


71 


71 


71 


72.4 


29 


70 


70 


69 


68 


68 


66 


66 


69 


72 


76 


78 


79 


82 


84 


84 


83 


82 


79 


76 


75 


74 


73 


73 


71 


74.4 


30 


71 


71 


71 


70 


70 


69 


69 


70 


71 


71 


72 


73 


73 


73 


74 


74 


73 


73 


73 


73 


71 


72 


72 


72 


71.7 


31 


72 
67.2 


71 
67.0 


69 

66.7 


68 
166.4 


68 
66. C 


67 
65.6 


66 
65.4 


66 
66.6 


71 
68.9 


76 
71.9 


77 
73.1 


79 
74.0 


80 


82 
74.9 


83 
75.0 


83 
74.7 


82 
74.2 


80 

72.9 


77 
71.6 


74 
70.6 


73 
69.8 


72 
69.0 


71 
68.4 


71 

67.9 


74 1 


Mean 


74.7 


70 \ 



30 

EXERCISE 6. 

against the side of the containing vessel. If under pressure, it is intelligible that such air 
should yield to the pressure and contract. Much confusion in the theory of the winds 
arises from the loose doctrine that warmed air rises and cooled air sinks. A good test 
between this and the view stated at the head of this paragraph is to isolate some air, 
warm it and cool it and note its behavior. 

56. Apparatus : A flask fitted with a rubber stopper, having a single hole through 
which a long glass tube is fitted, and a glass of water. 

Invert the flask, allowing the end of the tube to dip into the water. Note the level 
of the water in the glass and in the tube. Now warm the flask with both hands ; note 
and record what happens. What would have happened had there been no outlet? 
Carrying the apparatus out of doors or to the open window, causes what to happen? 
What would have happened had there been no outlet? Drawings should be made of the 
apparatus, showing the stand of water in glass and tube in all three stages of the 
experiment. What is your opinion of the sufficiency of the statement that warm air 
rises? Did it in this case? That cold air sinks? Did it? If warm air rises, why is 
not the upper air warmer than the lower? Is it? 

Where Air Expands Under Pressure and Does Work, it Loses Heat 

57. Two 250 cubic centimeter flasks are each fitted with a thermometer to record 
temperature, the first tightly stoppered and the second connected to a U tube containing 
mercury. A scale mounted by the U tube serves to register any variation in the height 
of the mercury. The heat is very satisfactorily furnished by two candles of the same 
size. Be careful in setting up apparatus to get all connections air tight, and that the 
candles are of the same size and mounted with the flame the same distance under the 
flasks (not less than four inches). After the apparatus has been carefully set up take 
the temperature, light the candles and record the temperatures in the two flasks every 
minute, also the height of the mercury in the U tube. Record it until no further varia- 
tion in the height of the mercury occurs. Tabulate your results. Explain any difference 
in the temperatures noted in the two flasks. Suppose we could apply the heat from the 
combustion of a unit of fuel to warm a quart of air enclosed in a glass flask with a rubber 
stopper and tube dipping into mercury, as in the experiment. Let us further suppose 
that no heat is lost, that the air expands with the heat, pushing the mercury down in the 
tube, and also becomes one degree warmer. Now if the experiment could be repeated 
with all the quantities and conditions the same, except that the quart of air was con- 
tained in a strong vessel that would not let it expand, the result would be that the air 
would rise in temperature more than one degree, although its original temperature was 
the same, the initial quantity of air the same, the original pressure the same, and the 
amount of heat used the same. The result may be stated thus : the amount of heat 
that somewhat warms air that is free to expand, will produce a greater rise in tempera- 
ture in the same quantity of air confined. If less warming is produced upon air that ex- 
pands, what becomes of the rest of the heat in this case? The answer is that it is used 
up in the work done. When the air in the flask expanded, it had to push the mercury 
up in the tube, and that was work. To do work energy is needed. The only energy at 
hand to do the work was the heat supplied, and whatever energy was devoted to expan- 
sion could not also appear as a rise in temperature. 



31 

Air is Cooled by Expansion 

58. Now if the flask of air that was closed by the mercury in the U tube could be 
placed under the receiver of an air pump and some of the air pumped out of the receiver 
the air within the flask would expand, would push down the mercury in the near side 
of the tube and up, of course, in the other. This would be doing work, but we are not 
now supplying heat to do this work with. If the temperature of the air in the flask were 
noted before and after the experiment, what should we see? Energy that was just now 
occupied in what we might call heat work — moving the air particles back and forth at 
the rate proper for the temperature— has now been diverted to lift a little mercury 
against gravity. Only a part of it, therefore, is now engaged in heat work, or, we may 
say, the air has been cooled in expanding against pressure. If a quantity of air is com- 
pressed into a strong vessel and allowed to stand until it has taken the temperature of 
the room, it will suffer a distinct fall of temperature if allowed to expand under pressure 
as in the previous experiment. In this case it has only its own heat to call on to do the 
work of expansion, and as soon as that is done the temperature falls. It appears, 
therefore, that not only does heat cause expansion, but that expansion taking place, as 
it usually does, against pressure, uses up heat and causes cooling. This must not be 
taken to mean that expanding air always falls perceptibly in temperature, the fall is 
only perceptible when no external heat is supplied to it, or not enough to do the work. 
When external heat is supplied, the temperature rises all the time the air expands. In 
thought only do we have a succession of events ; first, the air warmed x plus y degrees ; 
second, the air, expanding, uses up some of its heat and cools through y degrees, with the 
final result of a rise in temperature of x degrees and an increase in volume. In reality 
heating and expansion are simultaneous. Some of the heat is applied to the heating, 
while the rest is used in expansion. 

For the air that was not allowed to expand, all the energy supplied was applied to 
raising the temperature, which accordingly rose higher than that of the expanding air. 

Air is Warmed by Compression 

59. On the other hand when air is compressed by the application of force, the 
energy used is transformed into heat and the air warmed. When gases are mechani- 
cally compressed, provision has to be made by the circulation of cold water or otherwise, 
to get rid of the heat generated. (Tynda'll's Heat as a Mode of Motion, lecture I and III, 
may be read in this connection.) 

Geographic Applications 

60. All of the layers of air in which the phenomena of the weather take place, are 
under pressure from the atmosphere above. If this pressure diminishes, the air expands, 
and is thereby cooled. Conversely whenthe pressure increases, the air is compressed 
and warmed. As the winds move over the surface of the earth, at times they ascend 
and descend the slopes of the mountains. When they ascend they go nearer the surface 
of the ocean of air. In that case there is less air above them, so they are able to ex- 
pand and lift the air above, which cools the winds because of the work done. In gen- 
eral, AIR THAT RISES EXPANDS AND COOLS. When the winds descend they 
go deeper below the surface of the ocean ot air. As this puts more and more air above 
them, they yield to the increasing pressure, contract, and are warmed by this 
compression. In general, again, AIR THAT SINKS IS COMPRESSED AND 
WARMED. 



32 

Since the pressure of the atmosphere at various levels is pretty well known, it is 
possible to calculate these changes of temperature due to ascent and descent of air. They 
amount to 5.2° per thousand feet and are known as adiabatic temperature changes. They 
apply only to AIR that rises and falls. A person climbing a thousand feet up on the side 
of a mountain would not find it 5.2° cooler above unless the air went up with him. It 
often occurs to students at this point that these doctrines are contradictory. Descend- 
ing air is compressed and warmed, but since warmth causes air to expand, it may seem 
as if the work of compression would be at once undone by the action of. the heat gen- 
erated. The difficulty is apparent only. Heat does not cause expansion but a tendency 
to expand. Whether a gas expands or not depends on the pressure to which it is sub- 
jected. To say that descending air is compressed is to say that it has not enough ex- 
pansive energy, EVEN WITH WHAT IS ADDED TO IT BY THE HEAT OF 
COMPRESSION, to enable it to resist the pressure of the air above. 

It is often taught that cold, lofty mountains cool the warm winds that blow on them 
from oceans and thus make them drop their moisture as rain. We have seen that the 
cooling is really adiabatic cooling within the air itself and therefore not caused by the 
mountains. Observation at many observatories on mountains shows higher tempera- 
tures there than kites reveal at the same height in the free air. Furthermore, if it 
were not so, and the air were warmer than the mountain, since the air is constantly 
flowing over the mountains today, tomorrow, next year, next century and for thou- 
sands and thousands of years it is evident that such enormous volumes of warm air 
must rather warm the mountain than be cooled by it, for the hugest chain is of in- 
significant bulk beside such masses of air as that. 

Master and memorize the following argument : — 
The wind is moving lower air 
When :— 
wind comes to a mountain, wind goes by a mountain top. 

1 The mountain sends it up. 1 The earth pulls it down. 

2 Wind has less air above. 2 Wind has more air above. 

3 It expands and lifts air above. 3 Air above settles down on wind and com- 

presses it. 

4 This work cools wind. 4 This work warms wind. 

5 This forms clouds. 5 This dissolves clouds. 

EXERCISE 7— Cold Aloft. 

61. Calculate the diminution of temperature per thousand feet of ascent from the 
data in the following table. As an illustration of the method to be followed : Geneva is 
seen to be 2230 feet lower than Chamonix ; this by the printed table. Also 9° warmer. 
In this case therefore it was found to be 9° cooler for an ascent of 2230 feet, how much 
is that for every 1000 feet? 9°-^2.2=4.°l, nearly. 

After computation of the rate of decrease per thousand feet of ascent in each indi- 
vidual case in the foregoing table : — 1. What seems to be the nearest whole number of 
degrees to express the rate of diminution ? DO NOT take an average ; the figures are 
not comparable, for they are not all made at the same time of day. This decrease of 
temperature is due to the fact that as you ascend from the earth you go away from the 
immediate source of most of the heat of the air. If, however, AIR rises and cools by 



33 



Place 

Geneva 

Chamonix 

Pass (Col du GeantJ. 



Time 



Station and Elevation 



Temp. 



July 5-18, '88, Mean Values 
July 5-18, '88, Mean Values 
July 5-18, '88, Mean Values 



1312 feet 

3542 feet 

11152 feet 



73° 
64° 
37° 





Kite Observations 






Dodge City, Ks 


July 23, '98, 10 A. M. 
July 23, '98, 10 A. M. 
July 23, '98, 2:10 P. M. 
July 23, '98,2:10 P. M, 
June 29, '98, 10 A. M. 
June 29, '98, 10 A. M. 


Ground 

Kite 5795 

Ground 

Kite 5419 

Ground 

Kite 4477 


81° 


Dodge City, Ks 


59° 


Dodge City, Ks 


85.5° 


Dodge City, Ks 


61° 


Dodge City, Ks 


80° 


Dodge City, Ks 


67° 






Pierre, S. Dak 


June 22, '98, 11 A. M. 
June 22, '98, 11 A. M. 


Ground 

Kite 5492 


87° 




75 3° 








June 11, '9S, 11 A. M. 
June 11, '98, 11 A. M. 


Ground 

Kite 5351 


81° 


Lansing, Mich 


559 




Cleveland, O 


June 12, '98, 9 A. M. 
June 12, '98, 9 A. M. 
June 26, '98, 8:25 A. M. 
June 26, '98, 8:25 A. M. 


Ground 

Kite 5319 

Ground 

Kite 3146 


79.5° 
58° 
76° 
65° 


Cleveland, O 


Cleveland, O 

Cleveland, O 


Arlington, Va 


May 12, '98, 8:30 A. M. 
May 12, '98, 8:30 A. M. 
June 14, '98, 6 A. M. 
June 14, '98, 6 A. M. 


Ground 

Kite 8211 

Ground 

Kite 2143 


67° 

44.5° 
77.5° 
72 4° 



Balloon Observations 



Mean of all times and places. 



9840 
16400 
32800 



19° 
3° 

-67° 



expansion against pressure, its decrease of temperature is 5.2° per thousand feet of rise. 
2. That being the case, what would be the temperature which Geneva air would as- 
sume if lifted to Chamonix? 3. Under these circumstances would it weigh more or 
less per unit of volume than the Chamonix air? The following consideration will help 
you decide.— suppose you have two open flasks of the same size full of air at the same 
temperature. Warm one of them. What will happen ? Will air go in or out ? Will 
it weigh more or less? A good balance will easily show the difference. 4. What would 
happen to it? (See 2.) Try the same in several cases. 5. What do you find to be 
true? 6. From this would you conclude that cold air is always heavy, hot air alwavs 
light? 



34 

The United States Weather Bureau 

62. Every morning observations are taken of thermometers, wind vanes and other 
instruments at some ninety stations in various parts of the United States. The results, 
together with some contributed from neighboring countries, are combined by telegraph 
to make a daily forecast of the weather. The total cost of the service of the Weather 
Bureau to the nation is near a million and a half dollars a year. What do the people get 
for their money? Not certain forewarning of every rain. That the Weather Bureau 
cannot give. What we do get from the Weather Bureau, however, is worth many times 
the appropriation every year. It is a service in three forms: (1) The saving of life and 
property in ships on the seas and lakes by warning the people of dangerous storms,. 
(2) the saving of life and property along great rivers by warning the people of dangerous 
floods, and (3) the saving of perishable foods, growing or in transit, by warning the 
people of severe frosts. Vessels in port, on the great lakes or oceans, are warned by 
the Weather Bureau of every serious storm tha,t is liable to affect them. There are prac- 
tically no failures in these warnings. The slighter changes in the weather cannot be pre- 
dicted with certainty, but the great ones that endanger life, can be 
foretold with great accuracy, and none of them now take us unawares. Al- 
most equally great is the saving accomplished by the river service, notably in the Ohio 
and Mississippi valleys where many people live. No dangerous rise in these rivers but 
is foretold by the Weather Bureau in time for dwellers on the lowlands to escape to the 
higher land and carry movable property beyond the reach of flood. Even the probable 
hour and height of flood at various points is pretty well announced beforehand. A re- 
cent illustration was the Ohio flood of February 19, 1908. So many perishable foodstuffs, 
largely fruit and vegetables, are now constantly in transit across the country, so many 
grow in regions like California and Florida, liable to be visited by destructive frosts, that 
forewarning of all cold waves makes possible great saving of property by protecting 
growing crops from frost and warming or affording other artificial protection to those in 
transit. Reference might be made to the frost of January 20, 1908, in Florida. Ship- 
pers of such goods now rarely fail to enquire of the Weather Bureau about the tempera- 
ture conditions to be expected during the time of an important shipment. There is 
certainly no department of the national government that brings a handsomer return on 
an investment of the people's money. 

EXERCISE 8.— Drawing Isotherms. 

63. We shall best familiarize ourselves with the details of the daily weather map 
if we practice some parts at least of its construction. To this end we will use data 
telegraphed to Washington to construct a map of isotherms. 

Isotherms are lines drawn through places having the same temperature. 
They are commonly drawn at intervals of 10° through places having temper- 
atures evenly divisible by ten, as 0°, 10°, 20°, 30°, etc. Usually the temperatures 
given are either higher or lower than the desired temperature. In such cases do not 
merely draw the isotherm between the two places, one of which has a higher and one a 
lower temperature than the temperature desired, but make an exact estimate each time. 
We have 27° and 35° for instance and wish to place the isotherm of 30° in that neighbor- 
hood. We should place a point j/% of the distance from the place having a tempera- 
ture of 27° to the one having a temperature of 35° and through that point draw the iso- 
therm. 



35 

Making use of the above principle in drawing" isothermal lines, draw the isotherms 
for one of the days, the data for which are given below : 



K J^— 1 


Eleva- 
tion in 
feet. 


Pressure 


Tempera- 
ture 




Eleva- 
tion in 
feet. 


Pressure 


Temprra- 

TURE 




A 


B 


A 


B 


A 


B 


A 


B 


Father Point 


100 

100 

227 

293 

60 

97 

125 

314 

600 

768 

335 

123 

117 

112 

57 

48 

624 

609 

656 

730 

674 

714 

762 

628 

10C4 

43 

36 

22 

1147 

608 

734 

612 

617 

671 

824 

525 

359 

762 

399 


3040 
.40 
.38 
.42 
.42 
.43 
.44 
.43 
.30 
.39 
.42 
.42 
.42 
.41 
.41 

24 
.17 

23 
.32 
.30 
.28 
.36 

32 
.25 
.24 
.18 
.15 
.14 
.08 

05 
.13 
.17 
.16 
.28 
.18 
.22 
.13 
.21 
.05 


30 03 

.00 
29.64 
.55 
.66 
.67 
.73 
.67 
.75 
70 

.77 
.83 
.87 
.96 
.86 
.79 
.73 
.86 
.90 
.80 
29.88 
30.01 

29.98 

30.01 
03 
.12 

30.02 

29.97 
29.97 
30 01 
30.05 
.01 
.05 


-7 
-13 
20 
-4 
-1 
7 
9 
13 
10 
12 
7 
8 
20 
20 
26 
40 
21' 
17 
10 
20 
22 
15 
18 
28 
33 
46 
50 
63 
22 
17 
20 
20 
23 
28 
30 
31 
36 
37 
33 


43 


Dululb 

St. Paul 


702 

837 

720 

599 

963 

481 

54 

54 

1671 

757 

935 

13Q6 

1103 

2504 

1749 

2134 

1674 

1460 

3251 

2826 

5290 

1398 

1500 

2423 

2494 

2372 

5372 

3767 

2263 

2171 

4108 

5000 

1160 

1943 

4340 

330 

153 

153 


30.02 
29.96 
30.03 
30.04 
29.98 

29 86 
30.02 
29.87 

30 12 
.12 

30.12 

29 89 
29.85 
29.69 
29.77 

30 09 
30.12 
29.95 
30.01 
29 84 
29.95 
30.27 

.31 
.30 
.30 
.10 
.13 
.00 
.35 
.33 
22 
.31 
.31 
.40 
.36 
.23 
.20 
30.29 


.17 
.15 
.08 
06 
.13 
.06 
.03 
.01 
.43 
.43 
.32 
.34 
.20 
30 08 

29 98 
30.34 

.44 
.40 
.38 
24 

30 17 
30.27 

.24 

.27 

.25 

.36 

30.20 

29.88 

30.13 

.23 

30.18 

29.88 

29 98 
30.11 
29.99 

30 02 
30.00 
30.03 


28 

31 
31 
32 
33 
38 
48 
53 
00 
10 
23 
20 
30 
30 
51 
11 
15 
22 
22 
26 
26 
6 
7 
15 
21 
21 
20 
40 
8 
15 
25 
19 
17 
31 
18 
43 
37 
42 


40 


Chatham 


48 


Halifax 


50 
50 
56 
62 
62 
66 
49 
59 
59 


Lacrosse. 


53 


Quebec 


60 


Montreal 


Fort Smith 


63 


Albany 


71 


Boston 




75 


New York 


76 


Parry Sound 


41 


Buffalo 


Winnepeg 


41 


Oswego 




44 






48 


Philadelphia 


68 
71 
73 

11 

50 
49 
60 
61 
61 
64 
64 


56 


Norfolk 


Abi'ene 


64 

73 


Charleston 


Ou'ApDelle 


40 


Sault Ste. Marie... 


Bismarck 


43 


Alpena 


Pierre 


48 


Saugeen 


Rapid City 

North Platte 
Denver 


48 


Detroit 


55 


Toledo 


56 




Prince Albert 
Battleford 


41 




43 




Swift Current,, 
Havre 


43 
44 


Jacksonville 


75 


Miles City 


45 




El Paso 


50 


Key Vt est 


78 
37 
36 
39 


72 


White River 


Calgar) 


48 


Port Arthur 


Medicine Hat..., 
Helena 


46 

47 




Modena 


49 


Green Bay... 




Kamloops 


60 


Milwaukee ; 


56 
58 
65 
66 

70 
68 


Winnemucca 

Los Angeles 

Portland, Ore 
San Francisco ,,. 


50 


Chicago 


51 




57 
60 


Chattanooga 


58 


Memphis 









Surface Isothermals, and Sea Level Isothermals 

64. 




Fig. 15. Normal Surface Temperature for June 



If all the temperatures for the 
month of June for many years are aver- 
aged and represented by isothermal 
lines, the result is CLIMATIC and 
shows the distribution of temperature 
usual at that season. Such a map is the 
accompanying figure 15, showing nor- 
mal surface temperatures for the 
month. It is supposed to show the 
temperatures to be expected at any 
place in the country at any time. It 
fails to do so, however, at present, be- 
cause the number of points of observa- 
tion is entirely too small. Some sta- 
tions are high and therefore, cooler 



36 



than neighboring places, others in valleys are warmer than the country around. Iso- 
therms drawn from such data cannot expect to represent the country correctly. Thus 
two valley stations in the mountains might each have a temperature of 30 degrees. But 
the isotherm drawn from one to the other might very likely pass across a mountain 
range, several thousand feet above. The temperature up there may be nearly zero, yet 
the map reports it as 30 degrees. Any such map has this defect unless the observation 
stations are numerous enough to represent the actual topography, which is never the 
case. The difficulty is met by "Reduction to Sea Level." The air is known to be 
cooler and cooler as one ascends above the level of the sea. From kite and balloon 
studies and others along the slopes of mountains, it is seen that the temperatures 
of high places are lower than they would be if the ground were lower. A series of cor- 
rections has been prepared by which temperatures at all heights are reduced to the level 
of the sea. The United States Weather Bureau adopts the following values :■ — 

December to February l°.5per 1000 ft. 

March to May and September to November 2°.0 per 1000 ft. 

June to August 2°.5 per 1000 ft. 

Thus a place 5000 feet above sea level has a normal surface temperature for Junt 
of 62.5°. The reduction to sea level for that time and height is 5 times 2.5° or 12.5°. 
The corresponding sea level temperature is 75°. If all the values are so reduced to sea 
level, and a system of isotherms drawn with the resulting numbers we shall obtain the 

distribution of tem- 
peratures about as 
they would be if the 
whole surface of the 
country could be 
smoothed down to 
the level of the sea. 
Fig. 16 is such a map 
of sea level isotherms 
for June. Though it 
does not correspond 
to any actual condi- 
tions, it does enable 
us to learn the nor- 
mal surface tempera- 
ture at any point and 
any elevation. Thus 
the sea level June 
normal for Toledo is 
70°, the elevation 674 
feet. Subtracting 

2/3 of 25°, or 1.6°, we have a surface normal of 68.4°, about as shown in Fig. 15. Pike's 
Peak is at latitude 39°, longitude 105°. It is 14,000 feet high. What is the June tem- 
perature up there? 

EXERCISE 9.— Spells of Weather. 

65. Construct temperature curves for January, for both Ypsilanti and Havana, 
using the mean temperatures of the days as given in the right-hand columns of tables 




Fig. 16. Sea Level Normals for June 



November 



J^ nua 



March 




Fig. 17. A year's actual temperatures at Detroit and Ancon 



37 

53 and 54, calling each square of quadrille paper one degree vertically and horizontally 
one day. Both curves may be placed on one diagram. 1. Does any diurnal sun effect 
show in this curve? 2. Does either curve show that the air got steadily warmer or 
colder through the month? 3. Which curve shows the more distinct spells of weather? 
4. How many warm spells at Ypsilanti? 5. How many cold? 6. How many days 
did that make a spell last on an average? These spells are the special characteristic of 
our weather except, usually, in May, June, July and August. Now construct diurnal 
curves for both places with the mean hourly temperatures from the bottom of the tables. 
Put them on the same diagram, using the same temperature scale but calling one 
square horizontally one hour. This enables us to compare the diurnal temperature 
ranges with what we might call the spell ranges, the difference between the cold spells 
or the warm ones that follow or precede. 7. At which place is the spell range greater 
than the diurnal? 8. How many times as great? This, too, is characteristic, a feature 
of the climates of these places. At the one place temperature changes are mostly from 
daylight warmth to nightly cooling, at the other this signifies much less than change 
from warm spell to cold and back. At one of the places days may be even colder than 
nights, as on January 7th and 11th. 

EXERCISE 10. 

66. Figure 17 shows the maximum and minimum temperatures observed at 
Ancon, Panama canal zone, and Detroit, Michigan, every day from October 1, 1912 to 
October 31, 1913. 1. How many distinct cold spells, of at least three days' duration, 
can you count at Ancon? 2. How many at Detroit? 3. What is the greatest pecu- 
liarity of the year's temperatures in the canal zone? 4. How did Detroit's temperatures 
in its hottest month differ from those of Ancon? 5. Did Detroit ever have a whole 
month of Tropical temperatures? 6. A whole week? There were 15 occasions when 
it was hotter at Detroit than at Ancon. 7. Which of these dates can you make out on 
the diagram? 8. Which place has the greater daily range of temperature? 9. In 
what month does each place have the least range of temperature? It is caused by clouds 
each time. 

This exercise should help you to see that the "Torrid" zone is not so much a hot zone 
as a zone that is steadily warm and especially that it has nothing corresponding to our 
winter. In the year studied both places happened to have the same maximum tempera- 
ture of 96°. But Detroit has known a maximum of 104° and Ancon's highest (in a rec- 
ord of only 8 years) is only 97°. Further our "Temperate" zone temperatures are not 
temperate at all but characterized by violent changes, as in March when one week saw 
the temperature jump from 3° to 67°. It is the zone of spells of weather. 

Irregularity of Temperature Distribution in Longitude 

67. From the isothermal map it appears that places on the same parallel of latitude 
have differing temperatures. This is not only due to different elevations above the sea, 
but also because the sun's rays fall on surfaces so different even where the rays have 
the same inclination. Land and water do not heat up equally under the sun, nor do 
bare and grass-covered lands. The red and yellow desert of North Africa, the blue 
Atlantic, and the plant-covered lands bordering the Gulf, do not undergo equal heating, 
so it is not strange that the air above them has varying temperatures. A continent or 
large island, like Australia, Madagascar, New Zealand, or Great Britain is always 



warmer than the neighboring sea in summer and also cooler in winter; for the land not 
only heats up more under the sun's rays, but also cools off faster in winter. 

Seasonally and with the spells of weather that succeed each other in our latitudes 
very great differences in temperature result from the importation of southern and north- 
ern air on the wind. Spring is due with us, for instance, when the sun reaches a certain 
elevation in the sky ; it is apt to come with a week of south wind. 

Pressure 

68. It has been pointed out that we live at the bottom of the ocean of air just as the 
inhabitants of the sea bottom pass their lives at the bottom of the ocean of water. 
But the gaseous nature of our atmospheric ocean gives it great pecularities. A shell fish 
in deep water has always the same amount of water above him, and about him it is 
always still. There are tiny changes in the quantity of water as waves pass above, and 
there are slow movements of sidewise drifts and currents. Entirely insignificant, how- 
ever, both of these in comparison with what occurs in the air. We have very great 
differences in the amount of air above us and it moves about on the earth's surface 
with the high velocity of the storm winds. Some knowledge of the varying amount of 
air above is necessary to understand the winds. It is not possible to feel it directly; its 
manifestation is in that somewhat vague thing called air pressure, and the in- 
strument that shows it, the barometer. It is so grounded, however, on changes of tem- 
perature that we may form an idea of it very readily by noting temperature changes. 
Paragraph 69 will help the student see what a barometer is and how air pressure is only 
a vague name for the quantity of air over the spot being studied. 

We shall now regard the rising of the barometer as indicating that more air is 
coming to the region, its falling as signifying less air present, i. e., some air is going away. 

Balancing Columns, Water and Mercury 

69. Materials: 2 glass jars, 18 inches high, and 3 and l l / 2 inches wide, respectively, 
1 glass tube, 36 inches long, Y\ inch wide. 1 pound of mercury. 

Put some mercury in the bottom of the smaller jar, stand the glass tube in the mer- 
cury, and pour water upon the mercury in the jar until the water is 13 inches deep. 
Note what happens within the glass tube. Make a measurement of height above mer- 
cury in jar. If the water is now withdrawn with a siphon, notice what happens within 
the tube as the water level falls in the jar. In siphoning, the water should be run into 
an empty jar, so that if any mercury comes over it may not be lost. If the water in the 
service pipe contains lime or other salts, distilled water should be used. 

Repeat the experiment in the larger jar. When you have a column of , water 13 
inches deep over the mercury in this jar, how does it compare in bulk and weight with 
the water in the first experiment? Suppose we had a jar a foot wide, and put water in 
it 13 inches deep over mercury in which a tube had been previously placed, what would 
happen within the tube? 

Suppose a bowl of mercury with a tube standing in it were placed in a pond or tank, 
so that the mercury was just 13 inhces under the water surface, while the tube projected 
above the water surface, what would happen ? 

What one quantitative condition must always be fulfilled in these experiments to 
get a column of mercury to balance a 13-inch column of water? To balance any column 
of water? 



39 

In all these cases both fluids have been visible, but once we know the principle, the 
water might be concealed, and we could still judge of its height very accurately by the 
height of the mercury in .the tube. 

AYe might in the Same way balance a column of gas against the mercury. Thus 
the heavy violet vapors of iodine weigh t -jVt as much as mercury? How long a tube 
filled with iodine vapor would balance one inch of mercury? How many inches? How 
many feet ? In the calculation we might disregard the compression in the bottom of the 
column by the weight of the vapor above. That would require a long tube, indeed, but 
it would be conceivable. Although it Avould be balancing gas against liquid, both would 
still be visible on account of the violet color of the gas. But as long as the mercury is 
visible, the same balance might be made with a colorless gas like air. Air under 
standard conditions weighs TT5T7 as much as mercury. How many inches, feet 
and miles of air in a column would balance an inch of mercury ? 

A barometer is really a tube in which a column of mercury balances the atmos- 
phere of air. By the height of the mercury column we judge the height the air column 
would have if it were of uniform density and composition throughout. The mercury in 
the barometer at sea-level stands about 30 inches high. How high a column of homo- 
geneous air, equally dense from top to bottom, would that represent in miles? 

We have thought of a bowl of mercury in which a tube is placed and the whole 
lowered into the pond. As long as the tube projects above water, its walls keep the 
mercury within from experiencing the pressure or weight of the column of water that 
rests on the mercury in the bowl without. As for the atmosphere in these experiments, 
it presses on the mercury inside the tube and on the water without alike, so it is just 
the same as if it exerted no pressure at all. 

Now, our thought of the atmosphere is of a widespread layer of air resting upon 
the earth, thin or rare above where the high mountains reach up into it, thicker or denser 
below where the weight of 'the upper layers that rest upon it presses it together. There 
is probably air a hundred miles above the surface of the earth, yet remembering that the 
earth is 8000 miles through, while vastly the greater part of the whole atmosphere is 
compressed into the lower ten miles, we see that it is a relatively thin film, fairly com- 
parable to the skin of an apple. Let us now try to imagine a bowl of mercury with its 
tube set into this ocean of air just as we thought of another set into a pond. The tube 
must always be thought of as long enough to reach up through the whole thickness of 
the atmosphere. Thus there will be no 'air within the tube, it being kept out by the 
glass walls. The mercury rises within the tube to balance the weight of air without on 
the surface of the mercury in the bowl. The hundred-mile-long tube would not be 
needed. If its walls could be fused together a few inches above the top of the mercury 
in the tube so as to keep the air out, the balancing would go on just the same. If more 
air came to that neighborhod, as in the crest of a wave, the column of mercury within 
the tube must rise to balance it. That is essentially what a barometer is, and how it 
works. 

70. That "the air presses" is believed to be an easier conception for beginners than 
the "pressure of air." As a form of words both may mean the same thing, but only 
one reality, the air, is involved, and the first statement may be regarded as the direct 
statement of fact. The presure, on the other hand, has no real existence except as a 
word. It is not a thing at all. Suppose the result of the action be a broken window. 



40 

It is the air that breaks it and not the pressure. This is just as true as if we were talk- 
ing of a ball flung at a window. The ball really breaks the glass, though we may use a 
variety of other phrases about it, each of which may have some value of its own ; as, 
the force of the ball breaks the window, the momentum, etc., the glass was broken by 
the impact of the ball, a boy.broke the glass with a wild ball, the blow of the ball upon 
the window broke it. Yet upon examination it appears every time to be the ball that 
breaks the glass. All abstract nouns have the same indirect relation to reality. Thus 
in the sentence, "This man's influence in the community is powerful," the influence is 
the subject of the verb, but the man is the real agent. This appears in the direct state- 
ment, "The man influences the community strongly." "The wife's energy supple- 
mented the ability of the husband." "The energetic wife helped the able husband." It 
is not pretended that the direct form is universally preferable. In the last example the 
first or indirect statement is much better. But in cases where quantities enter that are 
to be measured and thought of as acting, there is a great gain for elementary presen- 
tation in the direct statement and the avoidance of the abstract noun. It is air that 
affects the barometer, and not pressure of the air. If more pressure does not imply 
more air, it means nothing at all. Of course there is no reason why anyone who has once 
become familiar with the instrument should avoid the convenient word. But, though 
entirely justified and in the very best use, it is often a cause of early misunderstanding. 

Barometer Corrections 

71. Unlike the thermometer, the barometer readings need correction before they 
are transferred to the weather map. The corrections are two, for temperature and 
elevation. Since mercury expands with heat, the amount of mercury needed at any mo- 
ment to balance the atmospheric column will measure more or less inches according 
as the instrument is in a cold or warm room. To have a means of comparing the read- 
ings of different instruments, it is necessaryto allow for the temperature by calculating 
what the length of the column of mercury would have been had the temperature been 
that of freezing water. This is called the reduction to freezing point and must be applied 
to all readings of good barometers. 

The reason for the second correction, the reduction to sea level, is that we desire to 
know the distribution of atmospheric pressures at some uniform level. That the 
pressure varies at different levels we know. To understand the winds it is necessary 
to find out whether it is constant at any one level. So the readings are always reduced 
to sea level. 

Read the thermometer and barometer outside the window and those within. Where 
is it colder? How much? Where is the barometer "higher?" How much? Divide the 
difference in barometer readings by the number of degrees difference in temperature to 
ascertain how much the outer barometer seems to have fallen per degree of greater 
cold outside. The published tables of corrections for temperature allow for the expan- 
sion of the mercury, the glass tube, and the brass scale and do NOT apply to a baro- 
meter with a wooden scale such as is used in these experiments. The wood is more 
affected by moisture than heat, but changes with absorbed moisture are too irregular to 
be calculated. 

EXERCISE 11.— Drawing Isobars 

72. Isobars are lines drawn through places having the same air pressure. They 



41 

are commonly drawn on weather maps for intervals of one-tenth of an inch through 
places having pressures ending in even tenths as 30.1, 30.2, 30.3, 30.4, etc. In many- 
places where pressures are given they are higher or lower than the desired pressure. 
In such cases do not merely draw the isobar between the two places, one of which has a 
higher and one a lower pressure than the pressure desired, but make an exact estimate 
each time. We have, for example, two places having pressures of 30.10 and 30.30 and 
wish to draw the isobar of 30.20 in that neighborhood. We should locate a point just 
half way between the two places and draw our isobar through that point because 30.2 
must necessarily lie just half way between 30.1 and 30.3. The method is the same one 
used in drawing isotherms. 

On -the weather map for January 20, printed in this book, what are the the press- 
ures at Duluth, Detroit, Buffalo, Chicago, and Winnipeg? What at the same places Jan- 
uary 22? What on May 27? 

Relation of Air Temperatures and Pressures 

73. The system of isobars drawn with the readings for data A shows a grouping 
of low barometers in the central valley, west of the Mississippi with higher barometer 
readings grouped over the Rockies and again over the Allegheny mountains ; for data B 
high barometers on the 100th meridian and low in the St. Lawrence valley. Remember- 
ing that the readings have been reduced to sea level, what thought about the depth of 
the air over various parts of the country would explain such distribution of pressure 
on the supposition that the temperature is the same everywhere? Does that suggest 
a level upper surface of the atmosphere like that of the ocean? Of course our supposi- 
tion is improbable. The temperatures are not the same everywhere. The isothermals 
show differences even on the same parallel of latitude. You have learned from the daily 
weather map, that there is definite association of temperatures with the areas of high and 
low barometer. You are, therefore, in a position to judge the sort of error involved in 
our assumption of uniform temperatures all over the country on dates A and B. What 
are the real conditons of temperature in the country that morning? As warm air ex- 
pands and occupies more space, while cold air contracts and occupies less, we must 
modify our previous thought about the depth of air in various places. What shall we 
now believe about the air surface? 

74. The relation between pressure and temperature is a causal one. The pressure 
varies because the heat varies. Suppose the air over the continent of Australia to be 
warmer than the air around. Being warm the air tends to expand and mound up there 
overhead. 1. Would this make the pressure there less? 2. Would it make the air 
there weigh less? 3. Would the barometers go up or down because of this tendency to 
expand? 4. Why not? 5. Is a bar of iron lighter or heavier when hot? 6. Why 
should a mass of air be? 7. Is it true that warm air is light? 8. If some air in a bag 
weighs a pound, will it weigh less when we warm it? The only sense in which warming 
makes it lighter is that it expands and occupies an amount of space that would at the 
lower temperature be occupied by a greater amount and weight of air. 9. What will 
happen instead? 10. If some air goes away above how will that affect the barometers 
below over the sea? 11. How in Australia? 12. Under such circumstances the winds 
will blow in toward Australia from all around. This actually happens every summer. 
13. Why? 14. Would you say such winds are caused by temperature or differences 
of temperature? 15. Which is the more immediate cause, difference of temperature 



42 

or difference of pressure? 16. What causes the difference of pressure? The sun's 
heat causes a change in the condition of the air. 17. What is this change? Motion is 
involved in this change, but it is motion within the mass and not motion of the mass. The 
familiar statement that hot air arises is convenient sometimes, like the statement that 
the sun rises, but neither is exact. The lower air is always much warmer than the air 
high above the earth, but it is usually quite content to stay below without any tendency 
to rise, being so compressed by the weight of the air above that is not so light, quart for 
quart, as it is. Expansion, with motion within the mass is the only direct result of heat. 
But this expansion gives an opportunity to another force to cause motion of the mass. 
18. What is this force? 19. Is the first tendency to motion of the mass active above 
or below? It is at this moment that change of pressure appears. The pressure of the 
air is merely a manifestation of its weight and cannot change unless the quantity of 
air changes. If air goes away there will be less air, less weight, and less pressure. And 
wherever more air goes there will be more more weight and more pressure. The depth 
of the atmosphere to sea level is to be thought of as fairly constant since an excess of 
depth anywhere at once begins to find a remedy by the action of gravity. 

75. Heat causes a tendency to expand; expansion gives gravity a chance to move 
off air above, this causes unequal pressures within and without the warm area in the air 
below, unequal pressure below sets the lower air moving or causes winds. Do the winds 
then generally move toward places that are cooler or warmer than places around? It is 
familiar that the sun is always high in the sky near the equator, causing greater heat- 
ing there than near the poles. Nearer the poles are alternate seasons of high sun or 
summer, and low sun or winter, when the rays more nearly graze the earth's surface 
and warm it much less. Thus the strip of highest temperature and lowest pressure mi- 
grates across the equator with the sun twice each year. We shall presently find winds 
and rainfall migrating similarly. The mercurial barometer should now be read daily 
and the results recorded in the note book. Saturday and Sunday readings may be taken 

from the barograph sheet posted every Monday. The barograph should also be glanced 
at each day to see whether the barometer is at the moment rising or falling, and this 
fact be recorded. 

EXERCISE 12.— Inferring Isotherms to Isobars 

76. By a study of our collection of mounted weather maps or the series printed in 
Figs. 26 to 28, determine which is warmer, the front or the rear of the cyclone. Notice 
how this is expressed by the isothermal lines. To discover this the student had best con- 
fine his attention to low pressure areas that are strongly developed and which are shown 
completely, i. e. are not partly over the ocean. From these same maps determine 
which have the lower temperatures associated with them — areas of high or low pressure. 
The temperatures you are here concerned with, are those along the same parallels of 
latitude. You are to note the temperature along the same east and west line through 
a cyclone or from cyclone to anti-cyclone. You will be helped by considering whether 
it becomes colder or warmer at a place where isotherms that pass to the south are 
bent northward toward it. Note the effect that areas of high or low pressure have upon 
the direction of the isotherms. After you have succeeded in determining to your satis- 
faction the temperature relations existing in the cyclone and between the cyclone and 
anticyclone, express it in isotherms on both the engraved maps of isobars accompanying 



43 




Fig. 18. Pressures for March 3, 1904. Isotherms to be added by the student with the help of 
temperatures marked at the eastern coast 

the exercise, Figs. 18 and 19. Draw your isotherms at intervals of 10°, using as your 
starting points the temperature given at three points on the eastern margin of the 
map and estimating for intermediate temperatures. Draw your isotherms just as though 




Fig. 19. Pressure system for January 19, 1904. Isotherms to be put in by the student 
with the help of temperatures marked at the east coast 



44 



the only factor causing them to deviate from a straight east and west line were the areas 
of high and low pressure, and assume that a difference of each tenth of an inch on the 
barometer will place the isotherm a tenth of an inch out of an east-west course, like a 
parallel, through the points on the east coast where the temperature is marked. 

Winds 

77. The wind is the lower air moving. The motion is from a region of high press- 
ure to one of low pressure, and these differences of pressure almost always have their 
cause in differences of temperature. Among the simplest cases are the continental winds 
of Australia, referred to in paragraph 74, and shown in the diagrams (Figs. 20 and 21). 



- t^~^ r ^ 


1 _^_^A 1 - 






J \ 


^ \ 11 


- 


TO 


\ ~?\ J 


0-\ — <vJ. 




Fig. 20. January 



Fig. 21. July 



How will the land and sea pressures near Australia compare in December? Such 
seasonal alternations of the winds from the sea and land are called MONSOONS. 
North America has less pronounced but perceptible monsoons. (Fig. 22 and 23). They 
are most strongly developed in the northern Indian Ocean. (Figs. 24 and 25). 2. In 




Fig. 22. Average winds of United States, July 



45 




Fig. 23. Average winds of the the United States, December 

what season will southern Asia be warmest? 3. When will it have the lowest pressure? 
4. Why does the southwest monsoon blow there in summer? 5. Why the northeast 
monsoon in winter? 




60 70 80 90 100 

Fig. 24. Winter monsoon, January, February 



46 

50 60 70 80 90 100 110 120 




Fig. 25. Summer monsoon, July, August 



EXERCISE 13.— Cyclonic Winds. 

78. By an inspection of the weather maps (Figs. 26 to 28) for Jan. 20, 21, and 22, 
1902, what would you decide to be the general movement of the air around areas of low 
pressure — toward or away from the center? 

2. On the map of Jan. 21, 1902, how do the winds seem to be blowing about the 
low pressure area centered over eastern Tennessee? 3. Are they blowing straight to- 
ward the center? 4. If not, to which side of the center, right or left? Look straight 
north of the area on Lake Erie. 5. If the winds there blew straight AT the area they 
would be north winds. 6. Are they? If they go west of south they turn to the right, 
i. e. to THEIR right of straight ahead. 7. Do winds at stations straight to west of Ten- 
nessee, go toward southeast (right) or northeast (left) ? 8. As you look at the other 
maps again, does the same thing seem on the average to be true? 

State in general terms the movement of the air around the cyclone. Illustrate by a 
diagram, using six arrows to show the direction of the wind, and show to the instructor. 
Make the shaft of each arrow straight and half an inch long. 



47 




48 





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53 

EXERCISE 14.— Anti cyclonic Winds 

79. Examine the weather maps for May 26, 27 and 28, 1902, and determine 
whether the air around the areas of high pressure seems to be moving outward or 
toward the center of the area. 

1. On the map for May 26, do you detect anything besides the outward move- 
ment of the air? 2. Do the winds blow straight out, to the right of straight out, or 
to the left of straight out? 3. Do you discover any verification of your conclu- 
sion on the maps for other days? 

State in general terms the movement of the air in the anticyclone. Illustrate 
by a diagram as you did for air movement in the cyclone. 

Land and Sea Breezes 

80. When such an alternation of winds is diurnal instead of seasonal, they are call- 
ed land and sea breezes. Like all winds these are named from their point of origin. 
They are observed on most sea shores and on many lakes, being distinct in summer on 
Lakes Huron and Michigan, on days of feeble general circulation of the air. In winter 
the land is usually colder than the lake, even by day, so the lake breeze is absent. 

Lake or sea breezes that blow by day to the heated land are always stronger than 
the land breeze of the night, mostly becausethe rougher land surface offers more resist- 
ance to the passing of the air than the water does. It is always the case that the wind 
blows faster on the water than on land. For the same reason, kites, balloons and clouds 
show the movements of the upper air to be much more rapid than the winds below. 
Mountain winds confirm us in this view of the effect of friction in retarding the wind at 
the earth's surface. 

Average wind velocity in miles per hour at various shore and inland stations : — 



Block Island 


17.2 


Key West 


10.5 




Boston 


11.8 


Salt Lake City 


6.0 




Chicago 


17.0 


San Francisco 


10.6 




Cincinnati 


7.7 


Wood's Hole 


15.8 




Galveston 


10.9 


Denver 


8.0 




Hatteras 


13.9 


Pikes Peak 


18.0 




Kansas City 


8.6 


Mt. Washington 


34.0 


(36.0 in winter) 



The Winds of Observation 

81. We should gather material for the study of the winds by noting the direction 
and force of the wind each morning with the principal changes during the day. We may 
use the data gathered from a wider area on the daily weather map, and we may note 
the effect of the prevalent wind on the trees. This is often well shown on fruit trees, 
which yield the more readily as the ground is kept soft by cultivation, unless, indeed, 
the farmer has been prudent enough to plant his trees leaning against the wind, as is 
sometimes done. In what direction does this make the trees lean with us? Select iso- 
lated trees in the country, to which the wind has free access, and note the unequal de- 
velopment of the branches. The best time to observe this effect is in the leafless season, 
when the growth of the twigs is seen to be much influenced. Most affected perhaps 
are the poplars, and after them the willow, maple, elm, buttonwood, hickory, oak, and 
black walnut, in order. The cottonwood appears to yield very little to the influence. 
Find examples of this influence of prevailing winds. If the wind observations have 
been kept since the beginning of the course, it now appears clearly that the west ones 



54 



are the more frequent. 1. What percentage 
the wind effect on the trees in the same direc 
in the northern belt of westerly winds. Th 
60 degrees of north latitude. 

There is a similar belt in the southern 
the progressive and energetic races of the 
observations to know that there are many 
laboratory exercise on the winds about areas 
every direction, it is true, but with two com 
were these? 



of all have you in that direction? 2. Is 
tion? The winds of observation for us are 
ey extend around the world between 30 and 

hemisphere and in these two regions live 
world. But we do not need to keep weather 
other winds than westerlies here. In the 
of low barometer we found them blowing in 
mon rules of conduct, so to say? 3. What 




EXERCISE 15.— Wind Effect on Trees 

Our winds are prevailing from the same general 
direction. This is shown plainly by many trees. 

Go from the city westward in open country. 
Examine the trees from the southward or northward. 
When you think you pereceive a wind effect, go to a point east or west of the tree. Is it 
now symmetrical? Sketch the tree from two directions at right angles. Observe and 
describe the wind effect on it. 

82. The diagram of planetary winds, Fig. 32, shows the average winds as they 
would blow on an earth without land. They are not real winds of the weather. None of 




Fig. 32. The winds as they would be on an ocean-covered globe 

our east winds show, for instance, since they are fewer than the west winds and disap- 
pear in the average. Also all land winds are weaker than sea winds because of the fric- 
tion of the surface of the land. So both trades and westerlies are much checked on 
lands. 



55 




Calcutta Nagpur 



Fig. 33. World Isobars 

The -summer and winter rainfall maps, Figs. 42 to 45, show ACTUAL winds of the 
world. 

EXERCISE 16— Monsoon Temperatures 

83. Construct curves of annual temperature at Calcutta and Nagpur, India, from 
the following data, using one square of the quadrille paper, vertically, for one degree, 
and two squares, horizontally for a month. 1. Locate both places on Fig. 25. Calcutta 

is in north latitude 22.5, east longitude 88.5, Nagpur in 21 
north, 79 east. 2. At what date has Calcutta its maxi- 
mum temperature? 3. When does the maximum come 
at Ypsilanti? 4. When at Nagpur? The sun is in the 
zenith of Calcutta twice, June 7 and July 3 ; in the zenith 
of Nagpur May 25 and July 18. 5. About what time 
should we expect the maximum temperature at Calcutta ? 
6. At Nagpur? You are to find out why the maximum 
temperatures in India come earlier than one would ex- 
pect. The following may help you. 7. From what di- 
rection does the wind blow in India in summer? 8. Upon 
what has this wind been resting before reaching India? 

9. Does this make the summer of India warmer or less warm than otherwise? 

10. What appears from the curve to have happened towards the end of May? 11. At 
what date did the summer monsoon begin to blow? 12. How did this affect the Nagpur 
thermometer? 13. Why does the maximum temperature come early at these two 
places? (Of course if something lowers the temperature at the time the marimum 
should occur the maximum is thereby madeto come earlier.) 



January 

February ... 

March 

April , 

May 

June 

July 

August 

September. 

October 

November. 
December.. 



64 
70 
80 
85 
85 
84 
83 
82 
82 
80 
73 
65 



68 
74 
83 
88 
94 
86 
80 
80 
80 
79 
72 
67 



56 

Water Vapor, Clouds and Rain 

84. Water vapor is always present in the air. Even in the desert enormous quan- 
ties of water are always present in this form. Water vapor is transparent and invisible. 
The bluest sky, the clearest air contains it. Clouds are made of little particles of water, 
not of water vapor. Mist is cloud seen from the inside. Cloud is mist seen from the out- 
side. The steam inside the tea kettle is invisible as would be noted were the kettle made 
of glass. Close to the spout nothing is seen to issue. Only a little way off appears the 
mist of water particles called steam. It really consists of water drops condensed from 
the steam by the cold air. Probably most of the water vapor in the air comes from the 
trade wind belts of ocean on either side of the equator. This map of the world, Fig. 34, 
shows the distribution of the Salter parts of the ocean surface. 1. What has the great 
saltness of these parts of the ocean to do with the supply of water vapor in the air? 



T 






20 40 60 60 100 120 




160 180 160 140 



?° 



20 



180 160 



Fig. 34. Saltness of ocean water. The saltest water is lined and the least salt is blank 

2. Are the trades growing warmer or colder as they advance? 3. Why? 4. Are 
they gaining in power to take up water? 5. Is the sky often cloudy in the trade winds? 
The percentage of cloudiness in Fig. 35 will enable you to answer the question. 




Fig. 35. Lined areas have cloudy sky more than half the time 



57 

85. Vapor is formed from water at all temperatures. The water particles are be- 
lieved to be in a state of rapid motion. Our thought of evaporation is that occasionally 
one of these particles near the surface plunges out into the air. This, as has been said, 
occurs at all temperatures, but naturally more at higher temperatures, when the particles 
are moving faster. When this process has gone on long enough to cause a great num- 
ber of particles to exist in the vapor condition, it is not difficult to believe that occasion- 
ally one of these particles plunges back into the water. This should happen oftener as 
the space above the water becomes fuller of vapor. But presently there must come a 
moment when as many plunge in in a given time as emerge. At this moment the great- 
est possible amount of vapor exists in the space and it is said to be saturated. If more 
heat be now applied the emergence of particles becomes more active and more vapor can 
be contained in the given space. If it be cooled, emergence is checked and the quantity 
of water vapor that can be contained in the space is diminished. In usual phrase warm 
air has a greater capacity for water vapor than cold air, though the air has nothing to 
do with it ; the same evaporation occurs into an empty space as into air and faster, per- 
haps because the air acts as a hindrance to the movement of the particles. 

86. Experiment has shown that air containing 4 grains of water vapor to the cubic 
foot is saturated at 50°. That is at that temperature 4 grains and no more of water could 
be evaporated into it. If cooled below 50° some of the vapor will take the form of dew 
or cloud. Experiments further show that a fall in temperature to 30° would condense 
about half the water vapor, while a rise to 70° would enable it to take up another 4 
grains to the cubic foot if it could get it. If it got no more water it would be said to 
have become drier in view of its increased capacity for moisture. Eor ordinary thought 
air is dry when it will dry other things. In this sense it is no part of drying air to take 
water away from it; on the contrary we might add two grains of water to the cubic foot 
while we raised it to 70°, and as it would still have a capacity of two grains of water it 
would be drier than it was at 50°. The effective moisture of the air is thus seen to be as 
much dependent on temperature as on water content. A better name for this sort of 
moisture is relative humidity. It is said to be 100 per cent, when the air is saturated, 
as is air at 50° with four grains of water vapor to the cubic foot, but the same air heated 
to 70° without gain or loss of water would have a relative humidity of 50 per cent, con- 
taining only four out of a possible eight grains. 

87. To illustrate actual values of relative humidity, the following table is inserted 
of average monthly temperatures and humidities observed at Detroit in 1898, at 8 a. m.. 
Eastern time : 



1898 



Tempera- 
ture 



Grains Vapor to 
1 Cubic Foot of Air 



Possibly Actually 



Relative 
Humidity 



Pints Water 
Room 2 1 



January ... 
February . 

March 

April 

May 

June 

July 

August 

September 
October.... 
November 
December. 



26.2 
24.1 
35.3 
40.8 
59.4 
66.1 
69.7 
67.8 
61.7 
49.1 
34.8 
25.4 



1.67 
1.53 
2.42 

2 95 
5.64 
7.11 
7 91 
7.48 
6.12 

3 97 
2. J 8 
1.62 



1.44 
1 41 
194 
2.01 
3.61 
5.19 
6.17 
6 13 
4.83 
3.30 
1.95 
1 38 



86 
92 
80 
68 
64 
73 
78 
82 
79 
83 
82 
85 



3.9 

3.8 

5.3 

5 5 

9.2 

14.2 

16.9 

16.7 

13 2 

9.1 

5.3 

3.8 



58 



At the average temperature observed in January, 26.2°, 1.67 grains of water vapor 
suffice to saturate a cubic foot of air, but as there were present only 1.44 grains the rela- 
tive humidity is said to be \%% or 86 per cent. If our room measures 42 by 
34 by 14 feet, multiplying the cubic feet in it by the grains of water to the cubic foot 
actually present in any month we shall get the number of grains of water present. Di- 
vide this by 7300, the number of grains in a pint, and thus verify one or two of the num- 
bers in the last column. It seems surprising to find so large a quantity of water contain- 
ed in the air. And the table shows that it is precisely in the summer months, when the 
sky is clear three-fourths of the time that the air contains most moisture, fully four times 
as much as in January when the sky is clear only a third of the time. Yet the summer 
air is drier, or better, the relative humidity is less, as the table shows, 1. How much 
vapor to the cubic foot can the January air still take up ? 2. How much the August 
air? Strange as it seems the clear skies of August contain much more water vapor 
than the cloudy skies of February. The desert of Sahara has about as much water vapor 
in its air in summer as moist England, yet the desert temperature is so high that the air 
is dry, i. e. the relative humidity is not more than forty or fifty per cent. 3. What rela- 
tive humidity is usual here? 

"Thus the air even above the dry ground of the desert contains a considerable 

amount of water vapor, brought from the neighboring seas 
and coast regions by air currents and by the diffusive power 
of the water vapor itself. The rainless character of the 
desert is caused, not by a lack of water vapor in the air, but 
by the absence of conditions leading to its condensation." 

88. The accompanying table contains the possible 
water contents at the given temperatures. 1. What was 
the water content in grains to the subic foot of the air in the 
room at time of the experiment? 2. How many pints of 
water? 

Construct a curve from this table, using one square of 
quadrille paper, vertically, for 2°, and horizontally for */> a 
grain of water vapor. 

Measuring Moisture in the Air 

89. Take the temperature of the air in the room and the water, which should have 
the same temperature, and will if it has stood in the room long enough. Dry the ther- 
mometer and again take the temperature of the air. Place a little water on the therm- 
ometer bulb and note what happens. Can you explain ? The warmth of the mercury is 
being used to do work. What work? Now wrap the bulb with the cloth which is 
twisted into a rude wick and dipped into the water in the tumbler. The temperature 
falls and in five or ten minutes will reach its lowest point. Note the temperature reached 
and by the following diagram ascertain the RELATIVE HUMIDITY. 

Dry 73°, wet 71°, difference, 2°, relative humidity 90 per cent. 

90. Human interest in the water vapor in the air is in relative humidity which af- 
fects our comfort, and precipitation, which conditions life. 1. What are the conditions 
that lead to the condensation of water vapor ? The fall of temperature that will be 
thought of as the cause, is due to some upward movement of the air and the expansion 
that must result. Such ascents occur in the equatorial regions, in cyclones and at 
mountain slopes. The last case has alreadvbeen referred to. 2. In the first two what 
lifts the air? 3. Are there any movements of the air round about that cause the cen- 
tral air to rise? 





Possible 


Tempera- 


No. of Grains of 


ture. 


Water Vapor 




per cu. ft. 


0° 


0.54 


10° 


0.84 


20° 


1 30 


30° 


1.97 


40° 


2.86 


50° 


4 09 


60° 


5.76 


70° 


7.99 


80° 


10 95 


90° 


14.81 


100° 


19.79 



59 






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60 



It is now seen that there are several belts about the earth with rain conditions. One 
has a good deal of uprising air at all times. 4. Where is this belt? 5. What are its 
rain conditions? In another belt the air rises only at mountain slopes. 6. What 
sort of skies and what sort of lands should prevail at other points in this belt? 
7. Which belt is it? Another has two different arrangements for causing the air to 
rise. 8. Which is this? Finally it is observed that two of these three belts occur 
necessarily in pairs. 9. Which ones? It is now possible to locate doldrum, trade- 
mountain and west-wind rainfall on the blank map. 



EXERCISE 17— Our 

91. Examine the table below of rainfall 
is the rainfall greatest? 2. In what least? 
ly rainfall (2.77 inches) is it least? 4. In 
the wettest month had less than the average 
is that? 6. Has summer or winter greater 
our crops? Construct a diagram of four ho 
left ends in the same vertical line. The len 
the rainfall of three consecutive months, one 
other group of three months. Let one-half 
rainfall. 



Irregular Rainfall 

at Lansing, Michigan. 1. In what month 
3. By what per cent of the average month- 
how many years does the table show that 

rainfall? 5. What per cent of all the years 
rainfall here? 7. Is that good or bad for 
rizontal lines one above the other with their 
gth of each line will represent the sum of 

for the three of greatest and one for each 
inch in the diagram represent one inch of 



Ykak 


Jan 


Fkb. 


Mar. 


Apr. 


May 


Junk 


July 


Aug. 


Sh.pt. 


Oct 


Nov. 


Dkc 


Ykar 


1880 


2 67 
2.27 
1.13 
098 
1.92 
1.59 
2 27 
3.36 
1.69 
1.67 
2.71 
1.07 
1.05 
1.84 
1.75 

2 66 
1 11 
3.62 

3 77 
2.05 
1.43 
1.69 

38 

1 54 
2.82 


1.85 

3 92 
2.59 

4 49 
3.24 

45 

1 64 

5 87 

1 74 
1.02 
1.85 

2 35 
1 64 
2.31 
1 67 
0.62 
1 08 

1 22 

2 16 

1 65 

2 84 
1 26 
0.56 

3 10 
1.53 


2.00 
2.14 
3 66 

34 
3.71 
6.40 
2.83 
1.30 
2.02 

1 14 
1.31 

2 48 
1.49 
3.78 
1.26 
1.14 
1.15 
3.20 

3 73 
.3.17 

2.20 
2.97 
4.12 
1.52 
3.87 


7.06 
1.65 
1.85 
1.89 

2 12 
2.38 
1.51 
0.98 
1.29 
1.70 

3 23 

2 45 
2.40 
5 30 

3 31 
1.12 
2 05 
2.43 
2.04 
1.93 
2 30 
2.29 
1.69 

4 40 
1 70 


6.81 
2.97 
4.33 
6.31 
4 34 
1.85 
3.00 
2.12 
3.65 
3.86 
6 22 
1.84 
6.31 
4 08 
6.51 
2.05 
2.67 
3.44 

2 16 
3.28 
4.25 
2.67 
3.91 
2.07 

3 60 


6 96 
3 66 
5 51 
9.91 

3 09 
5.88 
2.14 
1.45 
2.07 
3.65 

4 03 

2 26 
4.81 
7.19 
1.81 
1 24 
3.39 

3 6S 
4.55 
1.15 
2.19 
3.75 
7.07 
4.16 
2.79 


6.00 
1.63 
1 84 
10.12 
3.24 
2.04 
0.64 
1.68 
1 SO 
2.67 
52 
2.91 
3 08 
0.98 
1.45 
1.72 
7.10 
7.36 
1.46 
2.62 
5.09 
6 33 
6.99 
4.79 
2.15 


6 02*' 

2.05 

4.04 

0.21 

1.34 

6 75 

5.70 

0.93 

1.84 

18 

3.06 

5 27 

3.26 

73 

0.00 

5.38 

3 28 

2.0^ 

2.99 

33 

3 86 

3 24 

39 

5.68 

2.76 


4 13 
3 24 
1.07 
3.37 
2 71 
3.46 
6 05 
5.53 
2.06 
0.83 
2.39 
1.37 
2.80 
2.34 
2.76 
086 
6 27 
0.91 
2.53 
2.24 
1.27 
1 88 

5 66 
3.92 
2.35 


2 84 
5 60 
3.10 

3 64 
6.13 

3 60 

1 15 

2 28 
3.03 
75 

4 96 

77 
1.00 
4.55 

1 98 

87 
0.87 
2.14 
3.66 
3.11 
3.51 
4.87 

1 65 
1.99 
2.20 


2.38 
4.39 
1.75 
4 08 
1.60 
3.05 
1.37 

2 06 

3 33 
2 59 

2 91 

4 39 
2.61 
2.46 
1.05 

3 91 

2 98 

3 39 

2 60 

1 86 

3 88 
1.32 

2 30 
1.45 
07 


66 

1 76 
1 30 
0.93 
2.77 
2.86 
1.22 
2.5i 
1 25 
268 
1.35 
1 89 
1.61 
3 96 
1.14 
5.83 
0.72 
1.95 
1.27 
1.61 
0.47 
2.90 
2.32 
2.06 
1.27 


49 


1881 


35 


1882 


32 


1883 


46 


1884 


36 


1885 


40 


1886 


29 l A 


1887 


30 


1888 


26 


1889 


23 


1890 


3\V Z 


1891 


29 


1892 


32 


1893 


39 V 2 


1894 


25 


1895 


27 


1S96 


33 


1897 


35 


1898 


33 


1899 


25 


1900 


33 


1901 


35 


1902 


37 


1903 


37 


1904 


27 






Average 


2.00 


2.11 


2.52 


2.44 


' 3.77 


3 93 


3.45 


2.S4 


2. 88 


2 73 


2.55 


1 93 


33 1 







At Boston the annual rainfall is 45.4 in. 
distributed as in the table. 

Fill out the Lansing columns. 







BOSTON 


LANSING 






Inches Per Ct. 


Inches Per Ct 


Feb.. 


Mar., Apr. . 


. 11.4 25 




May, 


June, July. . 


. 10.5 23 




Auff., 


Sept., Oct.. 


. 11.5 25 




Nov 


., Dec, Jan.. 


. 12.0 27 





45.4 



100 



61 



Maps 

92. The ball shape of the earth makes it impossible to draw maps correctly on any- 
thing but a ball. Any map on flat paper is necessarily somewhat distorted. A familiar illus- 
tration is the cracking of a half orange peel that has been removed intact in its natural 
form, on pressing it down on the table. Another good one is had when you attempt to 
wrap a ball up in paper. Flat paper cannot be accommodated to it. Such surfaces — 
those to which a flat paper cannot be adjusted by mere rolling or wrapping, are known 
as warped. A trial, however, will quickly show that for a small part of the earth's sur- 
face, the disagreement between the ball surface and a plane is not very great. A circle 
of paper half an inch in diameter, placed upon a six-inch globe, comes near enough to 
resting upon the surface to make the part of the map traced through it fairly identical 
with that on the globe. Such a circle on that scale is 660 miles in diameter, about big 
enough to contain all the Great Lakes and the country about them ; the whole of the 
British Islands, or any European country except Russia, Sweden or Norway. So there 
are many maps in which the distortion is of little account. Maps of whole continents, 
however, are necessarily somewhat distorted, and no map of the whole world, or even a 
hemisphere, can help misrepresenting shapes and sizes. Different methods of map- 
drawing, or "projection," as it is called, are devised to render maps of large areas avail- 
able for various purposes, one considering the needs of the navigator, another that of 
persons wishing to compare areas, and others wishing a map that gives a comparative 
view of the whole world at once. The study of projection utilizes the highest skill of 
the mathematician. But simple constructions will give some good results. The device 
by which maps are drawn on the globe is the use of latitude and longitude, parallels and 
meridians. Something of the sort is rendered necessary by the fact that a ball has neither 
a beginning nor an end. 

93. Meridians and parallels cover the surface of a globe with a network of meshes. 
These are said to be ten-degree meshes when meridians and parallels alike are ten de- 
grees apart, four degree meshes when these are four degrees apart, and so on. On most 
maps meridians and parallels are the same number of degrees apart, but many globes 
have fifteen-degree spaces between meridians and ten-degree spaces between parallels, 
for purely mechanical reasons. The shapes of the meshes are different in different lati- 
tudes. If meridians and parallels are the same number of degrees apart what is the 
shape of the enclosed meshes near the equator? What near the poles? What at inter- 
mediate latitudes? 

EXERCISE 18 

To draw a map we must first prepare the right net. Let us try to draw Borneo, 
using a five-degree mesh and making it a ten-millionth as long 
or as wide as the real island. 

The northern parallel is 10° north, the southern one 5° 
south. 1. How many spaces shall we use in latitude? The 
western meridian is 105° east, the eastern one 120° east. 
2. East of what? 3. How many spaces shall we use in longi- 
tude? 4. How many meshes will there be in the finished 
map-net? The following table gives the dimension of the ten- 
Fig. 37. Bornec degree meshes of the actual world in inches, full size : 




62 





10° on 


slant height 


Lat. 


parallel 


for cone 





43,821,397 


infinite 


10 


43,159,992 


1,424,078,254 


20 


41,190,721 


690,100,982 


30 


37,982,129 


435,243,224 


40 


33,615,524 


299,636,802 


50 


28,223,172 


211,093,357 


60 


21,965,743 


145,324,237 


70 


15,032,175 


91,655,436 


80 


7,634,237 


44,415,856 



5. How many inches is a ten-millionth of ten 
degrees on the tenth parallel? 6. How many a 
ten-millionth of ten degrees on the meridian. 
7. How many five degrees in each case? Let us 
make the meshes squares of two inches on an edge. 
Because we are not using the exact values found, 
the scale of our map is not 1 : 10,000,000, but 1 : 10,- 
936,978. Do you see how that works out? 8. Con- 
struct a six-inch square and subdivide it into nine 
equal squares. 9. Number them as in the cut and 
make an outer frame two-tenths of an inch outside of the six-inch square. 10. Now 
draw Borneo on it faintly with a very soft pencil. Put dots in the middle of each 
mesh. They will help you draw the coast lines across the meshes. Notice where the 
coast line cuts the meridians and parallels and make these crossing points right before 
attempting to draw the coast line. When the coast line looks as good as you can make 
it darken it. On the finished map the coast should show more plainly than any other 
line. Parallels and meridians should be as fine and faint as you can draw them. They 
are only helps, the outline of the country is the real thing. 



Ten degrees of latitude is 43,747,944 inches 



EXERCISE 19. 

94. To make a ten-degree map net for North America on the scale of a hundred- 
millionth. Materials. You need now two drawing pencils, a HHH for points and lines, 
and a B for outlines of coasts or boundaries. Both need special sharpening to long, 
needle points, very much sharper than any point we use on a pencil for writing. You 
cannot make a good map without this special pencil point. Also a flexible paper rule 
divided into tenths of an inch and perforated with a small hole at the zero point for the 
point of the pencil so that you can draw circles up to a radius of 12 inches with it. A 
small celluloid triangle will be very useful 

1. As Fig. 38 shows, the northern latitude is 70°, 
the southern 10°. 2. What is the middle latitude? 
3. According to the table in paragraph 93, the tangent 
to the real world at latitude 40° is 299,636,802 inches 
long. 4. How long shall we take that? What is our 
scale? 5. How do we get three inches? 6. On a 
sheet of the blank paper detached from the back of the 
book, draw a straight line parallel to the long edges of 
the sheet through the middle. Construct a rectangle 
three inches high and four inches wide near the mid- 




dle of your paper 
long middle line. 



so as to be bisected by the 
7. At the middle of the frame 
place a dot. Call the line the 100th meri- 
dian and the dot its intersection with the 40th 
parallel. 8. Put another dot on the line three inches 
north of this dot. Put a faint little circle about this upper dot and call it the center of 
circles. 9. From this center draw a circle with a three-inch radius. It must pass 
through the lower dot. Why? The circle so drawn represents the fortieth parallel of 
north latitude. 10. We need other dots above and below 40° along the middle meri- 



Fig. 38. Net for horth America 



63 

dian for every tenth degree of latitude : 50°, 60°, and 70°, and 30°, 20° and 10°. 
11. How long is ten degrees of latitude? See table in paragraph 93. 12. How long 
shall we take it on our scale? 13. Place those dots. The table also tells us how far 
apart ten degree meridians are on the fortieth parallel. 14. How far shall we taken 
them? Shall we call it 33 or 34 hundredths of an inch? 15. Call our middle meridian 
the 100th west of Greenwich and place dots for meridians over to 30° west and to 170 
west latitude. 16. Now from the center of circles draw arcs of circles through all 
the dots along the middle line. Draw only those parts of the circles that can be drawn 
within the frame. 17. The meridians pass through the dots on the fortieth par- 
allel and the center of circles, but only that part of each is to be drawn which lies within 
the frame. 18. Number as in cut and add outer frame. 

EXERCISE 20. 

95. To draw Europe on the scale 1 :50.000.000. Northernmost latitude 70° N, south- 
ernmost 30°N. mid-latiude 50°N. From the table in paragraph 93 we get values for 
our scale of 10° latitude, 0.875 inches ; radius for 50°, 4.22 inches ; 10° longitude on the 
50th parallel, 0.564 inches. NOTE : These nets should be made of very fine lines, so 
fine as to be hard to see when held at arm's length. Beginners invariably make them 
too dark, too heavy, and above all, too wide, for they attempt to draw with a pencil point 
such as they write with. This work requires a pencil with a needle point, altogether too 
sharp and thin to write with. The first thing to do at each of these exercises, there- 
fore, is to sharpen the pencil. It will then need very light handling to preserve the 
point. Attention to this detail makes it possible to measure to hundredths of an inch. 

Directions: — 1. Draw a four-inch square near the bottom of the paper. 2. Num- 
ber the center of it 50°. 3. Draw the 20th meridian through the center, the full length 
of the paper. 4. Mark also the 70°, 60°, 40° and 30° points along the meridian, with 
the value of the 10° space given above. 5. Put a dot on the extended 20th meridian 
4.22 inches above the 50° point. This is the Center of Circles. 6. From this center 
draw arcs within the frame through all the points marked. Through the 50° point, 
make the arc across the whole sheet of paper, i. e., not merely within the frame as in the 
other cases. 7. Along this 50th parallel lay off spaces of ten degrees of longitude, five 
to the west and five to the east of the 20th meridian. 8. Connect each of these points 
with the Center of Circles with the ruler edge, and draw that part of the lines that falls 
within the frame. 9. Number meridians and parallels and enclose in a 4^-inch square. 
10. To accustom your eye to the outline of the continent of Europe make a tracing of 
it on rice paper from figure 6. 11. Draw Europe freehand on your net from Fig. 8. 

EXERCISE 21 

96. To draw South America on the scale 1-100,000,000. From 20° N to 60° S. 
What is the middle latitude? Take the values of radius for 20° and the ten-degree 
spaces from the table in paragraph 93. Frame measures 4 inches in latitude by 3 inches 
in longitude. As this continent is in the southern hemisphere, the meridians con- 
verge southward, so the frame should be drawn near the top of the paper, and the Center 
of Circles falls on the mid-meridian extended, below the frame. This mid-meridian is 
60° W. Outline of continent to be first traced and then drawn on the net- 



64 

EXERCISE 22 

97. To draw Africa. Scale 1-60,000,000. 1. The middle meridian (20° E) and 
the equator may be drawn as straight lines that cross in the middle of the paper, at right 
angles, and each about 6 l / 2 inches long. 2. Complete the square of which these two 
lines are diameters. It is the frame. 3. Lay off four ten-degree spaces along the 20th 
meridian on each side of the equator and draw straight lines parallel to the equator 
through these eight points for the parallels. 4. Lay off ten-degree spaces (longitude) 
along the equator, four to the east and four to the west. 5. Do the same on each par- 
allel, using always the ten-degree space of longitude for that parallel, which is taken 
from the table and reduced to our scale as usual. 6. Draw curves through these 
points with the help of the ruler. Number and draw map as usual. 

98. Scales. 1. How many inches in a mile? 2. A map on the scale 1-100,000,000 
has one inch where nature has a hundred million inches; how many miles is that? 
3. How many miles to an inch on a map of the scale 1-100,000,000? 4. How many 
miles to an inch on our map of Europe in paragraph 95? 5. How many on the map 
of Africa in paragraph 97? 6. How many miles to the inch on a scale of a millionth? 
7. If a map has 395 miles to an inch, what is its approximate scale-ratio? 8. What is 
the scale-ratio for a map with a hundred miles to the inch? 

EXERCISE 23 

99. To draw New Zealand on the scale 1-8,000,000 with a two-degree mesh. 1. Ten 
degrees on the meridian to that scale is 5.46 inches. How much is two degrees? 2. Sim- 
ilarly take from the table the values of two degrees on the 40th and 50th parallels. 

3. Draw the 172nd meridian through the middle of the paper parallel to the long edges. 

4. Lay off eight spaces along its middle portion, each 1.094 inches long. What do these 
spaces represent? The bottom one is to be numbered 50°. NOTE: When there is 
less than 20° of latitude in a country the parallels may be drawn as straight lines paral- 
lel to the equator without much error. Draw straight lines through the division points 
on the meridian and at right angles to" the meridian, extending two inches to the left of 
it and three to the right. 6. On the 40th parallel, toward middle of net, lay off spaces 
of 0.84 inch, two to the left and three to the right of the 172nd meridian. 7. On the 50th 
parallel lay off similar spaces of 0.706 inch. 8. Draw meridians through these points 
and number. 9. Draw New Zealand from Fig-. 39. 



'&■ 



100. Maps of most moderate-sized countries may be drawn as in exercise 23. The 
following lines show how to draw the parallels as curves. 

EXERCISE 24 

Repeat Nos. 1 to 4 of paragraph 99. 5. Number the dots along the meridian, put- 
ting 50° at the bottom and 34° at the top. 6. Draw perpendiculars through the 40° 
and 50° points, two inches to the left and three to the right of the 172nd meridian. 

7. Lay off divisions along these two lines as in numbers 6 and 7 of paragraph 99. 

8. Draw meridians and number 168° to 178° E. 9. Lay your ruler across the 172nd 
meridian, at right angles to it at the 36th parallel. 10. Draw a short line for about 
half a longitude space on each side of the meridian. 



65 




To make this wholly clear we may 
add that the line so drawn will cross 
the 172nd meridian at right angles and 
will extend about half way to the near- 
est meridians right and left. 11. Sup- 
pose you end the line so drawn about 
half way between 172 and 174. Do not 
lift the pencil point from the paper 
there, but rather bear on it lightly so 
that it forms a pivot about which you 
then turn the ruler edge, lifting the left 
end and lowering the right slightly, 
until the ruler is now perpendicular to 
the 174th meridian. 12. Now draw 
from the point where the pencil pivoted 
across the 174th meridian and on half- 
way to 176. In this way a line is drawn 
that looks very like a rurve and crosses 
all the meridians at right angles. 



171 IW 

Fig. 39 



Temperatures 

101. The usual data for temperatures are isothermal lines. They always represent 
temperatures reduced to sea level, though practically all geographies and physical 
geographies fail to mention that fact. It is the best way to draw isothermal lines. All 
meteorologists know it and how to use such a map, but teachers and school children do 
not. If a teacher tries to learn from such a map the temperature on the summit of the 
Himalayas she finds it to be 50° or 60° in winter and 80° or 90° in summer. Of course 
she knows there is ice and snow up there the year around and the map cannot be right. 
She does not know it has to be corrected for altitude before any of its indications become 
those of the actual surface, and finding it mentally indigestible she wisely lets it alone 
in all her work. Koppen's map on the contrary is for actual surface temperatures, and 
while it suffers certain defects inherent in all such maps, it does give a rough idea of 
the actual temperatures all over the surface of the earth and a fairly accurate one in 
those regions where men live. Note what our diagram indicates on the Himalayas. 

102. Temperatures. North America. Fig. 41 

1. What ocean shores are always cool? 2. What ocean has shores with hot sum- 
mer and cool winter? 3. What parts of Mexico are always hot? Why? 4. What 



66 



TEMPERATURE REGIONS 




Fig. 40 



SHADE 
Black 

Vertical lines 
I lorizontal lines 
Slanting lines 
Blank 



LEGEND 

TEMPERATURE 
Always Mild 



DETAILS 

Hottest month averages under 
68° coldest over 50° 
Always cool - Warmest month averages un der 50° 

Always hot - - Coolest month averages over 68° 

Hot summer and cool winter Averaging over 68° and under 50*° 
Summer hot and winter mild toward the equator ; 
Summer mild and winter cool toward poles. 



*For at least a month each. 



67 



OF THE WORLD 




Fig. 41 

Redrawn from Koppen as given by Ward in Bulletin Am. Geog. Soc, July, 1905, with slight alter- 
ations in the United States. 

It will help the eye in reading these diagrams if the student will now shade the Cool areas a very 
pale blue with a colored pencil,* the Hot areas a palered, and the Hot and Cool season regions with a 
red line on the first, fifth and ninth spaces between the slanting lines and so on with a blue one on the 
third, seventh and eleventh, thus making lines alternately red, white, blue, white and so on. 

In coloring the Cool areas do not overlook a small one between the thirtieth and fortieth parallels 
of north latitude. If the map were large enough to show them there would be other blue dots and 
lines on various other high mountain peaks and crests. 



"The six School Crayons in assorted colors sold in a box for five cents by the American Lead Pencil Co., 
for tinting maps. 



are excellent 



68 

temperature has Mexico City? 5. What temperatures prevail in most of Canada? In 
most of the United States? In Mexico? 6. What sort of summers and winters has 
Florida? Maine? 7. What three types of temperature occur on the California coast? 
8. Name three large cities with hot summer and cool winter. 9. Name two with mild 
summer and cool winter. 10. Name one with hot summer and mild winter. 

103. Temperatures. Europe. Fig. 40 

1. State England's summers and winters. 2. Name other countries of similar 
temperature. 3. State the temperature of Portugal. 4. Compare North Sea-Baltic 
countries with Mediterranean countries. 5. What different sorts of summers occur in 
Russia? Winters? 6. What temperature type is most widespread in Europe? 7. Name 
three large cities with hot summers and cool winters. 8. What ones can you name with 
mild summer and cool winter? 

104. Temperatures. Asia. Fig. 40 

1. What parallel approximately bounds most of cool Asia? 2. Locate and bound 
other cool regions. 3. What parallel bounds hot Asia? Exceptions? 4. Where are the 
hot-and-cool regions? 5. Explain the interruptions. 6. Name three countries that 
have hot summers and cool winters. 7. Where is it mild the year around? 8. State 
the temperature of India, China and Japan. 

105. Temperatures. Africa. Fig. 40 

1. Locate and bound and explain the mild areas. 2. Locate and bound the hot- 
and-cool regions. 3. Give the parallels approximately bounding the hot regions. 

4. Where in Africa are the cool winters and mild summers? 5. Explain and tell wheth- 
er people probably live there. 

106. Temperatures. South America. Fig. 41 

1. Locate and bound and explain the "always mild" regions. 2. Locate and bound 
the "always hot" regions. 3. Where, if the scale of the map were large enough to 
show it, might there be thin lines or dots of "always cool?" 4. What percentage of South 
America has hot and cold seasons? 5. Name a large city with hot summer and cool 
winter. 6. State the temperatures of Bogota, Lima, Rio Janeiro and Caracas. 

107. Temperatures. Australia. Figs. 40 and 41 

1. Where are the hot regions? 2. What regions are always mild? Why? 3. What 
towns have hot summer and cool winter? 4. State the temperatures of New Zealand. 

5. State the temperatures of Melbourne, Sydney and Wellington. 

108. Rainfall of June, July, and August, North America. Fig. 43 

1. Describe the two areas of scanty rain. 2. What national names might natural- 
ly be given to the two nearly separate parts of the area of abundant rain? 3. Why does 
it rain abundantly in Alaska and scantily on the California coast? 4. How much of 
North America has sufficient or abundant rain at this season? 5. Describe the distri- 
bution of rain in Alaska and explain with the help of the winds and a map showing moun- 
tains. 6. Describe the rainfall of the Pacific coast in three items. 7. Why have the 
West Indian and Arctic islands rainfall so different? 



69 

109. Rainfall of December, January and February. North America. Fig. 45. 

1. Describe the rainfall of the Pacific coast. 2. What rainfall characterizes the 
southern part of the continent at this season ? 3. What part and how great a part of 
North America has scanty rainfall? 4. To what sort of situations on the continent are 
the abundant rains limited? 5. What American states get their rain mostly in winter? 
6. In what sort of situations does most of the sufficient rain occur? 7. Name some 
states which seem to be characterized by summer rain. 

110. Rainfall of June, July, and August. Europe. Fig. 42. 

1. Name six regions of abundant rain. 2. Explain each of them. 3. What is 
the cause of the rainfall of Russia? 4. Describe the rainfall of Spain, Italy, and Ger- 
many. 5. What European sea has little rain on its shores? 6. What two countries 
have only scanty rainfall at this season? 

111. Rainfall of December, January and February. Europe. Fig. 44 

1. Describe six regions of abundant rain. 2. How much of Europe has scanty 
rain at this time of year? 3. Compare the distribution of rain in the Scandinavian, 
Iberian and Balkan peninsulas and in Asia Minor. 4. What country has its greatest 
drought at this season? 5. What country comes nearest to having the same rainfall 
summer and winter? 

112. Rainfall of June, July, and August. Asia. Fig. 42 

1. How much of the continent has abundant rain? (Include the islands.) 2. How 
far inland does the abundant rainfall extend ? (The north and south measure of each 
map net is 690 miles.) 3. Describe the shape, location and size of the large area of 
sufficient rain. 4. What is the grade of rainfall of the greater part of the continent at 
this season? 5. Locate the dry parts of Asia. 6. How does this resemble the distri- 
bution of rainfall in North America? 7. From what body of water did the Japanese 
rains evaporate? 

113. Rainfall of December, January and February. Asia. Fig. 44. 

1. What four points on the continent have abundant rain? 2. What other Asiatic 
regions? 3. Does this resemble the distribution of rainfall in North America in win- 
ter? 4. Why has India so much less rain than in summer? 5. From what waters did 
the Japanese rains of this season evaporate? 6. What two populous regions have suffi- 
cient or abundant rains at all seasons? 

114. Rainfall of June, July, and August. Africa. Fig. 42. 

1. Explain the rains of Madagascar. 2. Explain the southernmost rains of the 
continent. 3. Where are the northernmost rains? 4. What rainbelt do they belong 
to? 5. Why doesn't it rain in northwest and southwest Africa? 

115. Rainfall of December, January and February. Africa. Fig. 44 

1. Explain the northernmost rains. 2. Why are there no rains at the Cape of 
Good Hope? 3. What causes the rains of southeast Africa? 4. Explain the shift of 
the Doldrum rains since July. 5. Where is there abundant rain in both seasons? 



70 

6. In what month must the Nile he in flood? Allow a month or two for the water to 
get from the equatorial swamps into the river channels. 7. Do you perceive three Afri- 
can illustrations of seasonal migrations of rains? 

116. Rainfall of June, July, and August. South America. Fig. 43. 

1. Describe four patches of abundant rain. 2. What patches of trade-wind rain 
are there? 3. Which are clearly westerly wind rains? 4. How much of the conti- 
nent has scanty rain? 5. What parts of it? 6. Why is there so little rain on the Peru- 
vian coast? 

117. Rainfall of December, January, and February. South America. Fig. 45. 

1. How much of the continent has abundant rain? 2. Describe the rainfall of 
the Argentine Republic. 3. Describe the rainfall of Brazil. 4. Describe and explain 
the rainfall of Peru. 5. What regions have abundant rains in bn th seasons? 

118. Rainfall of June, July, and August. Australasia. Figs. 42 and 43. 

1. Is this summer rain? 2. What wind-belt yields most of it? 3. Why has the 
southeast corner more rain than the land ju^t west of the coast? (Compare eastern 
United States in Fig. 45.) 5. Why has the southern island of New Zealand more rain 
on the west than on the east? 6. Why not the northern island? Notice the relief of 
New Zealand. 

119. Rainfall of December, January and February. Australasia. Figs. 44 and 45 

1. Has Australia any westerly-wind rain at this season? 2. Has New Zealand? 
3. How may we know? 4. What are the two types of rain in Australia and where 
does each occur? 5. In what season has Australia most rain? 6. Is it like Asia in 
that? 

120. Plant Regions. North America. Fig. 47 

1. What percent of Canada is summer forest? Of the United States? 2. What 
three other types of vegetation occur in the United States in order of area occupied? 
3. Where shall a New York man go to get quickest to a wet tropic forest? 4. How 
much desert and grass land has the United States?* 5. What do we call the grass- 
lands of North America? 6. Why are they not as populous as the summer forests? 

7. Explain the forest of southeastern United States. 

121. Plant Regions. Europe. Fig. 46 

1. What two types of forest occur in Europe? Where? 2. What percentage of 
Europe is in summer woods? 3. Distinguish steppes from grass lands in Hungary and 
Russia. 4. Give reasons. 5. What North American types of forest are wanting? 

122. Plant Regions. Asia. Fig. 46 

1. To what rainfall, does the wet tropic forest correspond ? 2. What Asiatic coun- 
tries have deserts? 3. State the plant regions of China and India. 4. State the plant 
regions of Japan and Dutch East Indies. 5. What percentage of Asia has summer for- 
ests. What countries? 6. Where are the leathery leaf thickets? 



71 

123. Plant Regions. Africa. Fig. 46 

1. What types of forest are lacking? Why? 2. Equatorial Africa has many rivers. 
What report might a traveler along them make of the plant type there? 3. What is 
the real type? Why? See Fig. 11. 4. In what other parts of the world have we 
found the Cape Town vegetation ? 

124. Plant Regions. South America. Fig. 47 

1. What is the only plant type missing? Why? 2. What are the plant regions 
of Chile? 3. What those of the Argentine Republic? 4. In what wind belts are the 
wet tropic forests ? 5. What large country has most of the tropic forests? 6. Why 
are alpine plants so much more abundant than in North America? 
125. Plant Regions. Australasia. Figs. 46 and 47 

1. What sort of forests prevail in the thickly settled parts of Australia? 2. Where 
are the leathery leaf thickets found? 3. Explain the forests of the north. 4. Why 
should New South Wales and the southern island of New Zealand have plant regions so 
contrasted in position? 



* It has long been a vexed queston as to the absence of trees in a soil which seems to be most suitable for their 
development.. .Probably the most ancient explanation was the occurrence of prairie fires, but it seems evident that some 
general natural condition rather than an artificial one is responsible for such an extensive area. A possible explanation 
is as follows: The extensive plains of the West develop the strong and dry winds which prevail over the prairie region, 
and this brings about extremes of heat and drouth, in spite of the character of the soil. In such conditions a tree in a 
germinating condition could not establish itself. The prairies, therefore, represent a sort of broad beach between the West- 
ern plains and the Eastern forests. The eastward limit of the prairie has probably depended upon the limit of the dry 
winds, which are gradually modified as they move eastward, until they cease to be unfavorable to forest growth. The 
forest does not begiin abruptly upon the eastern limt of the prairie, but appears first a clump of trees, with interspersed 
meadows, and finally as a dense forest mass. Of course, the forest display of the eastern border of the prairie has been 
immensely interfered with by man. — Coulter, Plant Relations, page 236-8. 



72 



RAINFALL OF THE WORLD IN JUNE, JULY 




Fig. 42 



SHADE 


RAINFALL 


uled lines - 


Abundant 


ots - - - 
lank - - 


Sufficient 
Scanty 



DETAILS 

More than ten inches of rain and melted snow in the three 

months. 
From six to ten inches in the three months. 
Less than six inches in the three months. 



73 

AND AUGUST (INCLUDES MELTED SNOW) 



Fig. 43 



After Supan. 



It will add much significance to the diagrams if the student will now tint with pale red the shaded and 
dotted areas north of the tropic of Cancer, 23%°, north as symbolic of summer or warm season rains, and 
with pale blue the shaded and dotted areas south of the tropic of Capricorn, symbolizing cold season or 
winter rains. That the zone within the tropics remains uncolored means that it does not have true summer 
and winter. 



74 



RAINFALL OF THE WORLD IN DECEMBER, JANUARY 




No. 44 
LEGEND 



SHADE 
Ruled lines 

Dots - - 
Blank 



RAINFALL 
Abundant 

Sufficient 
Scanty 



DETAILS 



More than ten inches of rain and melted snow fall in the three 
months. 

From six to ten inches in the three months. 

Less than six inches in the three months. 



75 
AND FEBRUARY (INCLUDING MELTED SNOW) 



No. 45 



After Supan. 



It will add much significance to the diagram if the student will now tint with a pale shade of blue the 
ruled and dotted areas north of the tropic of Cancer, 23%° north latitude, as symbolic of winter or cold 
season rain, and the similar areas south of the tropic of Capricorn with pale red, symbolizing summer or warm 
season rains. The inter-tropical region remains uncolored, as being without true winters and summers. 



76 



PLANT REGIONS 




SHADE 

1. Black ----- 

2. Black Spots - 

3. Dots ------ 

4. Black Bars 

5. Black Triangles - - - - 

6. Circles - 

7. Stars of sixty degrees like a snowflake 

8. Broken lines - 

9. Small Dots - 



No. 46 

LEGEND 

VEGETATION 
Wet Tropic Forests 
Wet Season Tropic Forests 
Tropic Open Woods 
Sub-Tropic Wet Forests 
Leathery Leaf Thickets 
Summer Forests 
Alpine Plants 
Grass Land or Steppes 
Tundra 



77 



OF THE WORLD 




4. 



Fig. 47 

After Schimper DETAILS 

Warmth and rains at all seasons. Air plants abound. Forests are quite impassible 
Less dense. A season of drouth compels trees to drop their leaves and rest, Along the streams this does 

not happen. Temperature still high. Air plants numerous. 
Warm, but severe seasonal drouth allows only isolated trees in broad expanses of bush or grass. Continuous 

forest along streams only. 
Less luxuriant than near the equator. Evergreen ; but interspersed are trees that drop their leaves, not in 

dry, but in a cold season — winter. 
Always in regions of winter rain, 30° or 40° from the equator. The leaves are tough enough to withstand 

considerable summer drought. Oleanders are typical. Trees moderate sized, gnarled and less abundant 

than shrubs. Trees stunted by getting water enough for growth in the cold season only. 
Moderate rain and winter cold severe enough to arrest growth or cause leaves to fall. These forests 

may usually be traversed without hewing a path, but have fine trees which get their growth in a moist 

summer. 
Stunted plants that live on cold, windy mountain summits. 

With forests along the streams. Increasing drought changes grass land to steppe, the steppe to desert. 
Low shrubs and herbs that imperfectly cover the ground which is frozen ten months in the year. 




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